Reconstruction for Congenital Absence of the Fifth Metacarpal.

We report a case of an isolated congenital absence of the right fifth metacarpal with ring and little finger syndactyly in a 6-year-old girl without other ipsilateral limb anomalies or phenotypic disorders. The patient underwent amputation of the hypoplastic right little finger with reconstruction of the ulnar collateral ligament of the ring finger metacarpophalangeal joint as well as hypothenar muscle transfer. She has returned to normal childhood activities without limitation at 3 months after surgery. Absence of the fifth metacarpal is a rare congenital anomaly without clear recommendations regarding reconstructive options. This case discussion supplements the current literature by describing an unusual presentation of this hand anomaly while supporting individualized management to maximize functional and cosmetic results.

Minimalistic approach to enhanced recovery after pediatric scoliosis surgery.

PURPOSE: Prior studies of enhanced recovery protocols (ERP) have been conducted at large institutions with abundant resources. These results may not apply at institutions with less resources directed to quality improvement efforts. The purpose of this study was to assess the value of a minimalistic enhanced recovery protocol in reducing length of stay (LOS) following PSF for adolescent idiopathic scoliosis. We hypothesized that accelerated transition to oral pain medications and mobilization alone could shorten hospital length of stay in the absence of a formal multimodal pain regimen. METHODS: AIS patients aged 10-18 who underwent PSF at a tertiary pediatric hospital between January 1, 2014 and December 31, 2017 were reviewed. The study population was further narrowed to consecutive patients from a single surgeon's practice that piloted the modified ERP. Reservation from key stakeholders regarding the feasibility of implementing widespread protocol change led to the minimal alterations made to the postoperative protocol following PSF. Patients were divided into either the Standard Recovery Protocol (SRP) or Enhanced Recovery Protocol (ERP). Primary variables analyzed were hospital LOS, complications, readmissions, and total narcotic requirement. RESULTS: A total of 92 patients met inclusion criteria. SRP and ERP groups consisted of 44 (47.8%) and 48 (52.2%) patients. There was no difference between the two groups with regard to age, sex, and ASA score (p > 0.05). Fusion levels and EBL did not differ between treatment groups (p > 0.05). PCA pumps were discontinued later in the SRP group (39.5 ± 4.3 h) compared to the ERP group (17.4 ± 4.1 h, p < 0.0001). Narcotic requirement was similar between groups (p = 0.94) Patients in the SRP group had longer hospital stays than patients in the ERP group (p < 0.0001). 83% of the ERP group had LOS ≤ 3 days compared to 0% in the SRP group, whose mean LOS was 4.2 days. There was no difference in complications between the groups (2.2% vs 6.0%, p = 0.62). Readmission to the hospital within 30 days of surgery was rare in either group (2 SRP patients: 1 superior mesenteric artery syndrome, 1 bowel obstruction vs 0 ERP patients, p = 0.23). CONCLUSION: In this cohort, minor changes to the postoperative protocol following surgery for AIS led to a significant decrease in hospital length of stay. This minimalistic approach may ease implementation of an ERP in the setting of stakeholder apprehension.

Disparities in Pediatric Scoliosis: The Impact of Race and Insurance Type on Access to Nonoperative Treatment for Adolescent Idiopathic Scoliosis.

BACKGROUND: Adolescent idiopathic scoliosis (AIS) has evidence-based, nonoperative treatments proven to be effective with early diagnosis and prompt treatment. The purpose of this study was to identify potential disparities in access to nonoperative treatment for AIS. Specifically, we sought to determine the interaction of socioeconomic factors on a major curve magnitude and recommend treatment at the initial presentation. METHODS: A retrospective review of AIS patients who underwent surgery at a single tertiary pediatric hospital between January 1, 2013 and December 31, 2018 was conducted. Patients were divided into 2 groups for comparison: patients with public insurance (PUB) and those with private insurance (PRV). Primary variables analyzed were patient race, Area Deprivation Index (ADI), major curve magnitude, and treatment recommendation at the initial presentation. Univariate and multivariate analyses were conducted to identify the predictors of the major curve magnitude at presentation. RESULTS: A total of 341 patients met the inclusion criteria; PUB and PRV groups consisted of 182 (53.4%) and 159 (46.6%) children, respectively. Overall, the major curve magnitude at presentation was significantly higher in PUB compared with PRV patients (50.0° vs. 45.1°; P =0.004) and higher in Black patients compared to White patients (51.8 vs. 47.0, P =0.042). Surgery was recommended for 49.7% of the PUB group and 43.7% of the PRV group. A lesser number of PUB patients had curve magnitudes within the range of brace indications (≤40°) compared to PRV patients (22.5% vs. 35.2%, respectively; P =0.010). The odds of having an initial major curve magnitude <40 degrees were 67% lower among Black patients with public insurance compared to Black patients with private insurance (OR=0.33; 95% CI: 0.13-0.83; P =0.019). CONCLUSION: This study demonstrated disparity in access to nonoperative treatment for pediatric scoliosis. Black patients with public insurance were the most at-risk to present with curve magnitudes exceeding brace indications. Future work focused on understanding the reasons for this significant disparity may help to promote more equitable access to effective nonoperative treatment for adolescent idiopathic scoliosis. LEVEL OF EVIDENCE: III.

The Feasibility of Utilizing Malunion Criteria to Limit Radiographs After Spica Casting for Pediatric Femur Fractures.

BACKGROUND: There are no existing guidelines regarding the timing or frequency of postoperative radiographs following spica casting for pediatric femur fractures. The purpose of this study was to evaluate established femoral malunion criteria as a potential screening tool to limit postoperative radiographs by identifying patients at risk for unacceptable alignment in the early treatment period. METHODS: A retrospective chart review was conducted for pediatric femoral shaft fractures presenting to a tertiary pediatric referral hospital from 2012 to 2017. Pediatric femur malunion criteria were applied to radiographs at initial presentation, first follow-up visit, and final follow-up visit. The primary outcome was a change in management based on radiographic findings in the early postoperative period. Secondary outcomes included radiographic measures, number of follow-up visits, and complications. RESULTS: Of 449 consecutive pediatric femur fractures treated at our center, 149 patients aged 1 to 4 years (mean age: 2.5±1.6 y) met inclusion criteria. At initial presentation, 36.9% (55/149) of patients met malunion criteria. Only 4.0% (6/149) of patients had a change in management following initial closed reduction and spica cast application due to radiographic findings at subsequent follow-up. Of these patients, 67% (4/6) were identified on preoperative imaging, and 83.3% (5/6) were identified by their first clinic appointment. Four of the 149 patients were converted to definitive surgical fixation, and 2 patients required cast wedging due to either unacceptable fracture shortening or coronal/sagittal angulation. CONCLUSIONS: Routine early postoperative radiographs may not be necessary for all pediatric femur fractures managed with closed reduction and spica casting. The value of this study is that it is the first to demonstrate the feasibility of limiting postoperative radiographs using a preoperative screening tool. However, the established femoral malunion criteria utilized in this study were limited in their predictive value, and further work is necessary to improve the sensitivity and specificity before widespread clinical application. LEVEL OF EVIDENCE: Level IV.

Proximal tibia fracture dislocations: Management and outcomes of a severe and under-recognized injury.

INTRODUCTION: Proximal tibia fracture dislocations (PTFDs) are a subset of plateau fractures with little in the literature since description by Hohl (1967) and classification by Moore (1981). We sought to evaluate reliability in diagnosis of fracture-dislocations by traumatologists and to compare their outcomes with bicondylar tibial plateau fractures (BTPFs). METHODS: This was a retrospective cohort study at 14 level 1 trauma centers throughout North America. In all, 4771 proximal tibia fractures were reviewed by all sites and 278 possible PTFDs were identified using the Moore classification. These were reviewed by an adjudication board of three traumatologists to obtain consensus. Outcomes included inter-rater reliability of PTFD diagnosis, wound complications, malunion, range of motion (ROM), and knee pain limiting function. These were compared to BTPF data from a previous study. RESULTS: Of 278 submitted cases, 187 were deemed PTFDs representing 4% of all proximal tibia fractures reviewed and 67% of those submitted. Inter-rater agreement by the adjudication board was good (83%). Sixty-one PTFDs (33%) were unicondylar. Eleven (6%) had ligamentous repair and 72 (39%) had meniscal repair. Two required vascular repair. Infection was more common among PTFDs than BTPFs (14% vs 9%, p = 0.038). Malunion occurred in 25% of PTFDs. ROM was worse among PTFDs, although likely not clinically significant. Knee pain limited function at final follow-up in 24% of both cohorts. CONCLUSIONS: PTFDs represent 4% of proximal tibia fractures. They are often unicondylar and may go unrecognized. Malunion is common, and PTFD outcomes may be worse than bicondylar fractures.

Atypical osteochondroma of the lumbar spine associated with suprasellar pineal germinoma: A case report.

BACKGROUND: Osteochondromas are the most common benign bone tumor, accounting for 36% of benign bone tumors. Often found within the appendicular skeleton, osteochondromas of the spine are rare, comprising 4% to 7% of primary benign spinal tumors. CASE SUMMARY: We report a case of a solitary lumbar osteochondroma in an 18-year-old male with a history of a suprasellar pineal germinoma treated with combined chemotherapy and radiation. He underwent mass excision and partial laminectomy with the ultrasonic bone scalpel (Misonix, Farmingdale, NY, United States) at the L5 Level without the use of adjuvants. The patient returned to work and full activities without back pain at 3 mo postoperatively. CONCLUSION: Osteochondromas are common tumors of the appendicular skeleton but rarely occur within the spine. This case discussion supplements current osteochondroma literature by describing an unusual presentation of this tumor.

Effect of Nanoscale Ce0.8Gd0.2O2-δ Infiltrant and Steam Content on Ni-(Y2O3)0.08(ZrO2)0.92 Fuel Electrode Degradation during High-Temperature Electrolysis.

Studies of Ni-yttria-stabilized zirconia (YSZ) fuel electrode degradation mechanisms in solid oxide electrolysis cells (SOECs) are complicated by the different possible Ni-YSZ microstructures and compositions, and the variations in the H2/H2O ratio encountered in an electrolysis stack. Here we describe a life testing scheme aimed at providing survey results on degradation as a function of the H2O-H2 composition, with life tests carried out at five different steam contents from 90% to 10%. A Ni-YSZ-supported symmetric cell geometry is employed both with and without infiltrated nanoscale gadolinia-doped ceria (GDC). Impedance spectroscopy is utilized to observe changes in electrochemical characteristics during the life test, and a transmission-line-based equivalent circuit is used to model the data. Post-test electrode microstructures were observed. The results suggest that the GDC infiltrant reduces the electrode polarization resistance and provides more stable electrode polarization over a range of conditions.

The Impact of Cast Immobilization on Return to Daycare.

BACKGROUND: Children who are prohibited from returning to daycare (RTD) after treatment with cast immobilization place an increased burden on parents and caregivers. The purpose of this study was to assess the impact of cast immobilization on RTD. Specifically, we sought to determine the prevalence of RTD after orthopaedic immobilization based on daycare facility policy. METHODS: This was a survey study of randomly selected daycare facilities servicing a total of 6662 children within 10 miles of a major metropolitan city center. The 40-question survey included information on daycare policies and experience caring for children treated with orthopaedic immobilization. The survey also included questions about daycare type, enrollment, and geographic location. Photographs of the types of immobilization were embedded in the survey to facilitate understanding. Daycare facilities were randomly selected based on a power analysis to estimate a 50% prevalence of RTD after spica casting within 10% margin of error. RESULTS: Seventy-three daycare facilities completed the survey study. The average child-staff ratio was 5:1 and most daycare facilities (78%) did not have a nurse on staff. Predetermined policies regarding RTD after injury were available at 81% of daycares. Twenty-eight (38.5%) facilities had encountered a child with a cast in the previous year. The rate of RTD for children with upper limb injuries was 90.5% compared with 79% for lower limb injuries (P=0.003). Spica casts showed the lowest RTD rate: single leg (22.5%), 1 and a half leg (18%), and 2 leg (16%) (P<0.0001). Experienced daycare facilities (>5 y) had a higher RTD rate compared with less experienced facilities (P=0.026). CONCLUSIONS: The ability to RTD is dependent on immobilization type. Children with long leg and spica casts are disproportionately restricted when compared with other cast types. At minimum, surgeons should consider the socioeconomic implications of orthopaedic immobilization. There is also a need for orthopaedic involvement in policy formation at the local level to provide standardized guidelines for re-entry into childcare facilities following orthopaedic immobilization. LEVEL OF EVIDENCE: Level IV.

Simulation of the Electrochemical Impedance in a Three-Dimensional, Complex Microstructure of Solid Oxide Fuel Cell Cathode and Its Application in the Microstructure Characterization.

Electrochemical impedance spectroscopy (EIS) is a powerful technique for material characterization and diagnosis of the solid oxide fuel cells (SOFC) as it enables separation of different phenomena such as bulk diffusion and surface reaction that occur simultaneously in the SOFC. In this work, we simulate the electrochemical impedance in an experimentally determined, three-dimensional (3D) microstructure of a mixed ion-electron conducting (MIEC) SOFC cathode. We determine the impedance response by solving the mass conservation equation in the cathode under the conditions of an AC load across the cathode's thickness and surface reaction at the pore/solid interface. Our simulation results reveal a need for modifying the Adler-Lane-Steele model, which is widely used for fitting the impedance behavior of a MIEC cathode, to account for the difference in the oscillation amplitudes of the oxygen vacancy concentration at the pore/solid interface and within the solid bulk. Moreover, our results demonstrate that the effective tortuosity is dependent on the frequency of the applied AC load as well as the material properties, and thus the prevalent practice of treating tortuosity as a constant for a given cathode should be revised. Finally, we propose a method of determining the aforementioned dependence of tortuosity on material properties and frequency by using the EIS data.

Outcomes for Hand Burns Treated With Autologous Skin Cell Suspension in 20% TBSA and Smaller Injuries.

In order to address the confounder of TBSA on burn outcomes, we sought to analyze our experience with the use of autologous skin cell suspensions (ASCS) in a cohort of subjects with hand burns whose TBSA totaled 20% or less. We hypothesized that the use of ASCS in conjunction with 2:1 meshed autograft for the treatment of hand burn injuries would provide comparable outcomes to hand burns treated with sheet or minimally meshed autograft alone. A retrospective review was conducted for all deep partial and full-thickness hand burns treated with split-thickness autograft (STAG) at our urban verified burn center between April 2018 and September 2020. The exclusion criterion was a TBSA greater than 20%. The cohorts were those subjects treated with ASCS in combination with STAG (ASCS(+)) vs those treated with STAG alone (ASCS(-)). All ASCS(+) subjects were treated with 2:1 meshed STAG and ASCS overspray while all ASCS(-) subjects had 1:1, piecrust, or unmeshed sheet graft alone. Outcomes measured included demographics, time to wound closure, proportion returning to work (RTW), and length of time to RTW. Mann-Whitney U test was used for comparisons of continuous variables and Fisher's exact test for categorical variables. Values are reported as medians and 25th and 75th interquartile ranges. Fifty-one subjects fit the study criteria (ASCS(+) n = 31, ASCS(-) n = 20). The ASCS(+) group was significantly older than the ASCS(-) cohort (44 [32-54] vs 32 years [27.5-37], P = .009) with larger %TBSA burns (15% [9.5-17] vs 2% [1-4], P < .0001) and larger size hand burns (190 [120-349.5] vs 126 cm2 [73.5-182], P = .015). Comparable results were seen between ASCS(+) and ASCS(-), respectively, for time to wound closure (9 [7-13] vs 11.5 days [6.75-14], P = .63), proportion RTW (61% vs 70%, P = .56), and days for RTW among those returning (35 [28.5-57] vs 33 [20.25-59], P = .52). The ASCS(+) group had two graft infections with no reoperations, while ASCS(-) had one infection with one reoperation. No subjects in either group had a dermal substitute placed. Despite being significantly older, having larger hand wounds, and larger overall wounds within the parameters of the study criteria, patients with 20% TBSA burns or smaller whose hand burns were treated with 2:1 mesh and ASCS overspray had comparable time to wound closure, proportion of RTW, and time to return to work as subjects treated with 1:1 or piecrust meshed STAG. Our group plans to follow this work with scar assessments for a more granular picture of pliability and reconstructive needs.

Intraoperative Burden of Flexible Intramedullary Nailing and Spica Casting for Femur Fractures in Young Children.

BACKGROUND: Spica casting (Spica) remains the widely accepted treatment of closed femoral shaft fractures in young children aged 6 months to 5 years. In some centers, there has been a recent trend towards surgical fixation of these fractures with flexible intramedullary nails (FINs). Despite numerous studies evaluating both Spica and FIN treatment of femoral shaft fractures, there remains a paucity of data regarding patient burden during the intraoperative period. The purpose of this study was to compare the intraoperative burden, defined as anesthetic exposure, fluoroscopic duration, and radiation load, between Spica and FIN treatment of femoral shaft fractures in young children. METHODS: A retrospective chart review was conducted for pediatric femoral shaft fractures presenting to a tertiary pediatric referral hospital from 2012 to 2017. Comparison groups included pediatric femur fractures treated with Spica and those treated with FIN. Outcomes included anesthetic exposure, fluoroscopy duration, and radiation exposure. In addition, length of stay, clinic visits, and complications were recorded. RESULTS: Of 449 consecutive pediatric femur fractures treated at our center, 143 patients ages 2 to 6 years (mean age 3.8±1.4 y) met inclusion criteria. The Spica group contained 91 patients; FIN contained 52 patients. Mean anesthetic exposure was less for Spica compared with FIN [45.1 min, 95% confidence interval (CI): 38.0-52.3 vs. 90.7 min, 95% CI: 80.5-100.8 min; P<0.001]. On average, Spica procedures required less fluoroscopy time compared with FIN (15.4 s, 95% CI: 4.8-26.0 vs. 131.6 s, 95% CI: 117.6-145.6 s; P<0.001). Mean radiation load was less for Spica compared with FIN (1.6 mGy, 95% CI: 0.6-2.6 vs. 6.9 mGy, 95% CI: 5.7-8.1 mGy; P<0.001). There was no difference in length of hospital stay (P=0.831), follow-up visits (P=0.248), or complication rate (P=0.645) between Spica and FIN groups. The most common complication was skin irritation for Spica (18.7%) and symptomatic hardware for FIN (17.3%). CONCLUSIONS: The findings of this study suggest that pediatric patients with femoral shaft fractures experience an increased intraoperative burden when treated with FIN compared with Spica. Treatment with FIN was associated with increased exposure to anesthesia, fluoroscopic duration, and radiation load despite similar complication rates when compared with Spica. LEVEL OF EVIDENCE: Level III.

Comparison of Short-leg and Long-leg Casts for the Treatment of Distal Third Tibial Shaft Fractures in Children.

BACKGROUND: Long-leg casts (LLCs) are an established treatment for pediatric tibial shaft fractures including fractures involving the distal third. There is a paucity of literature assessing the use of short-leg cast (SLC) for tibial shaft fractures. The purpose of this study was to determine if SLC were as effective as LLC for the treatment of pediatric distal third tibial shaft fractures. METHODS: A retrospective review was conducted on consecutive distal third tibial shaft fractures treated at a tertiary pediatric hospital from 2013 to 2018. Exclusion criteria included midshaft and proximal fractures of the tibia, distal fractures that violated the tibial physis or plafond, and pathologic fractures. We compared primary outcomes of time to weight-bearing, time to union, and final angulation between LLC and SLC groups. RESULTS: Eighty-five patients aged 5 to 17 years (mean age: 9.2±3.2 y) met inclusion criteria, including 50 LLC and 35 SLC patients. Time to weight-bearing for SLC (3.3±0.6 wk) was shorter compared with LLC (6.4±0.7 wk, P<0.0001). Overall, fractures treated with SLC had a shorter time to the union (7.4±0.9 wk) compared with LLC (9.0±0.9 wk, P=0.026) without statistical differences in final angulation at the time of union. There was a higher percentage of cast complications in the LLC treatment group (12%) compared with SLC (6%). CONCLUSIONS: SLC demonstrated earlier time to weight-bearing and shorter time to fracture union when compared with LLC. Surgeons should consider SLC and early weight-bearing for the treatment of distal third tibial shaft fractures in children. LEVEL OF EVIDENCE: Level III-retrospective comparative study.

Use of Autologous Skin Cell Suspension for the Treatment of Hand Burns: A Pilot Study.

Purpose: Autologous skin cell suspension (ASCS) is a valid alternative and adjunct to split-thickness skin grafting (STSG) for treating burns. Limited data exists regarding the use of ASCS for hand burns. We hypothesized that using ASCS in hand burns shortens healing time with no difference in complications and less donor site morbidity. Methods: This was a retrospective chart review of second- and third-degree hand burns treated at a level 1 Trauma and Burn Center from 2017 to 2019. Study groups included patients with hand burns treated with ASCS in combination with STSG and those treated with STSG alone. Outcomes included time to re-epithelialization, return to work, length of hospital stay, and complications including reoperation, graft failure, and infection. Results: Fifty-nine patients aged 14 to 85 years (mean age 39 ± 15 years) met inclusion criteria. The ASCS treatment group comprised 37 patients; STSG comprised 22 patients. Mean follow-up time was 14 ± 7 months. The ASCS treatment group had a larger mean percent total body surface area (TBSA) (22% ± 14% vs 6% ± 8%; P < .05). There was no difference in time to wound re-epithelialization between both groups (ASCS, 11 ± 4 days vs STSG, 11 ± 5 days). Mean length-of-stay was 23 ± 13 days compared to 10 ± 13 days (P < .05) between the ASCS and STSG groups, respectively. No patients in the ASCS group required reoperation, whereas 2 patients in the STSG group required such for an infection-related graft loss and a web space contracture release. On multivariable analysis adjusting for TBSA, ASCS was associated with an earlier return to work (P < .05). Conclusions: ASCS is safe and effective in treating hand burns. ASCS was associated with similar rates of re-epithelialization, earlier return to work, and no difference in complications compared with STSG.Type of study/level of evidence: Therapeutic IV.

Endoscopic Proximal Median Nerve Decompression: An Alternative Treatment for Pronator Syndrome.

Proximal forearm median nerve compressive neuropathy, termed as pronator syndrome, is difficult to diagnose and often overlooked. Its symptoms include vague proximal volar forearm pain that may be associated with paresthesia and numbness in the median nerve distribution. Weakness is typically not present. The treatment of pronator syndrome is largely nonsurgical, consisting of activity modification, anti-inflammatory medication, corticosteroid injections, stretching, and periods of splinting. Surgery is indicated when conservative therapy fails; however, there is no consensus on the treatment approach or technique. Most decompressions are performed using an open technique through a variety of incisions. Recently, endoscopic approaches have drawn an interest. This article describes a technique for endoscopic proximal median nerve decompression that enables the complete decompression of the median nerve in the distal aspect of the arm and proximal aspect of the forearm through a small incision, potentially minimizing surgical morbidity and reducing healing time.

Comprehensive Enhancement of Nanostructured Lithium-Ion Battery Cathode Materials via Conformal Graphene Dispersion.

Efficient energy storage systems based on lithium-ion batteries represent a critical technology across many sectors including consumer electronics, electrified transportation, and a smart grid accommodating intermittent renewable energy sources. Nanostructured electrode materials present compelling opportunities for high-performance lithium-ion batteries, but inherent problems related to the high surface area to volume ratios at the nanometer-scale have impeded their adoption for commercial applications. Here, we demonstrate a materials and processing platform that realizes high-performance nanostructured lithium manganese oxide (nano-LMO) spinel cathodes with conformal graphene coatings as a conductive additive. The resulting nanostructured composite cathodes concurrently resolve multiple problems that have plagued nanoparticle-based lithium-ion battery electrodes including low packing density, high additive content, and poor cycling stability. Moreover, this strategy enhances the intrinsic advantages of nano-LMO, resulting in extraordinary rate capability and low temperature performance. With 75% capacity retention at a 20C cycling rate at room temperature and nearly full capacity retention at -20 °C, this work advances lithium-ion battery technology into unprecedented regimes of operation.

Degradation of nano-scale cathodes: a new paradigm for selecting low-temperature solid oxide cell materials.

Oxygen electrodes have been able to meet area specific resistance targets for solid oxide cell operating temperatures as low as ∼500 °C, but their stability over expected device operation times of up to 50 000 h is unknown. Achieving good performance at such temperatures requires mixed ionically and electronically-conducting electrodes with nano-scale structure that makes the electrode susceptible to particle coarsening and, as a result, electrode resistance degradation. Here we describe accelerated life testing of nanostructured Sm0.5Sr0.5CoO3-Ce0.9Gd0.1O2 electrodes combining impedance spectroscopy and microstructural evaluation. Measured electrochemical performance degradation is accurately fitted using a coarsening model that is then used to predict cell operating conditions where required performance and long-term stability are both achieved. A new electrode material figure of merit based on both performance and stability metrics is proposed. An implication is that cation diffusion, which determines the coarsening rate, must be considered along with oxygen transport kinetics in the selection of optimal electrode materials.

Three-Phase 3D Reconstruction of a LiCoO2 Cathode via FIB-SEM Tomography.

Three-phase three-dimensional (3D) microstructural reconstructions of lithium-ion battery electrodes are critical input for 3D simulations of electrode lithiation/delithiation, which provide a detailed understanding of battery operation. In this report, 3D images of a LiCoO2 electrode are achieved using focused ion beam-scanning electron microscopy (FIB-SEM), with clear contrast among the three phases: LiCoO2 particles, carbonaceous phases (carbon and binder) and the electrolyte space. The good contrast was achieved by utilizing an improved FIB-SEM sample preparation method that combined infiltration of the electrolyte space with a low-viscosity silicone resin and triple ion-beam polishing. Morphological parameters quantified include phase volume fraction, surface area, feature size distribution, connectivity, and tortuosity. Electrolyte tortuosity was determined using two different geometric calculations that were in good agreement. The electrolyte tortuosity distribution versus position within the electrode was found to be highly inhomogeneous; this will lead to inhomogeneous electrode lithiation/delithiation at high C-rates that could potentially cause battery degradation.

Degradation of (La(0.8)Sr(0.2))(0.98)MnO(3-δ)-Zr(0.84)Y(0.16)O(2-γ) composite electrodes during reversing current operation.

Reversing-current operation of solid oxide cell (La(0.8)Sr(0.2))(0.98)MnO(3-δ)-Zr(0.84)Y(0.16)O(2-γ) (LSM-YSZ) oxygen electrodes is described. Degradation was characterized by impedance spectroscopy in symmetric cells tested at 800 °C in air with a symmetric current cycle with a period of 12 hours. No change in cell resistance could be detected, in 1000 h tests with a sensitivity of ∼1% per kh, at a current density of 0.5 A cm(-2) corresponding to an overpotential of 0.18 V. At a current density to 0.6 A cm(-2) (0.33 V overpotential) measurable resistance degradation at a rate of 3% per kh was observed, while higher current/overpotential values led to faster degradation. Degradation was observed mainly in the ohmic resistance for current densities of 0.6, 0.8 and 0.9 A cm(-2), with little change in the polarization resistance. Polarization degradation, mainly observed at higher current density, was present as an increase in an impedance response at ∼30 kHz, apparently associated with the resistance of YSZ grain boundaries within the electrode. Microstructural and chemical analysis showed significant changes in electrode structure after the current cycling, including an increase in LSM particle size and a reduction in the amount of YSZ and LSM at the electrode/electrolyte interface - the latter presumably a precursor to delamination.

Three-dimensional microstructure of high-performance pulsed-laser deposited Ni-YSZ SOFC anodes.

The Ni-yttria-stabilized zirconia (YSZ) anode functional layer in solid oxide fuel cells produced by pulsed laser-deposition was studied using three-dimensional tomography. Anode feature sizes of ~130 nm were quite small relative to typical anodes, but errors arising in imaging and segmentation were shown using a sensitivity analysis to be acceptable. Electrochemical characterization showed that these cells achieved a relatively high maximum power density of 1.4 W cm(-2) with low cell resistance at an operating temperature of 600 °C. The tomographic data showed anode three-phase boundary density of ~56 µm(-2), more than 10 times the value observed in conventional Ni-YSZ anodes. Anode polarization resistance values, predicted by combining the structural data and literature values of three-phase boundary resistance in an electrochemical model, were consistent with measured electrochemical impedance spectra, explaining the excellent intermediate-temperature performance of these cells.