Cumulative Sum Analysis of Learning Curve Process for Vaginal Natural Orifice Transluminal Endoscopic Surgery Hysterectomy.

STUDY OBJECTIVE: This study aimed to evaluate the learning curve of vaginal natural orifice transuminal endoscopic surgery (vNOTES) hysterectomy in expert minimal invasive and vaginal surgery team. DESIGN: This is a cohort study on a retrospective analysis. SETTING: Department of Obstetrics and Gynecology of Cannizzaro Hospital in Catania Italy. PATIENTS: First 50 women underwent vNOTES hysterectomy between February 2021 and February 2022. INTERVENTION: vNOTES hysterectomy performed by a team with optimal skills in laparoscopic and vaginal surgery. MEASUREMENT AND MAIN RESULTS: Primary outcome was surgical time. Secondary outcomes were intraoperative and postoperative complications, length of hospitalization, and first 24-hour postoperative pain. All patients underwent hysterectomy for benign indications: 27 fibromatosis, 13 metrorrhagia, and 10 precancerous. Concomitant procedures have been bilateral adnexectomy in 35 cases and bilateral salpingectomy in 15 cases. The median age was 51 years (range, 42-64). Median body mass index was 26 kg/m2 (range, 21-42). The median operative time was 75 minutes (range, 40-110). The median hospital stay was 2 days (range, 1-4). There was 1 intraoperative adverse event (bladder lesion) and 1 postoperative grade 3 complication (hemoperitoneum). The median visual analog scale score for pain assessment during the first 24 hours after surgery was 3 (range, 1-6). The experience in our surgical center with the first 25 vNOTES hysterectomies showed an accumulation of initial experience in the first 5 cases with stable operating time and a gradual reduction of mean operating time in the subsequent 17 surgeries. The learning curve plotted by cumulative sum analysis shows 3 phases: phase 1 of competence (cases 1-5), phase 2 of proficiency (cases 6-26), and phase 3 of mastering the procedure (after the 31st case) with the management of more complex cases. CONCLUSION: vNOTES hysterectomy is a feasible and reproducible approach for benign indications with a short learning curve and low rate of perioperative complications. For a team skilled in minimally invasive surgery, 5 cases are required to rich competence and 25 to rich proficiency in vNOTES hysterectomy. Mastering phase, with the introduction of more complex cases, should be addressed after 30 surgeries.

Removal and Reoccurrence of LLZTO Surface Contaminants under Glovebox Conditions.

The reactivity of Li6.4La3Zr1.4Ta0.6O12 (LLZTO) solid electrolytes to form lithio-phobic species such as Li2CO3 on their surface when exposed to trace amounts of H2O and CO2 limits the progress of LLZTO-based solid-state batteries. Various treatments, such as annealing LLZTO within a glovebox or acid etching, aim at removing the surface contaminants, but a comprehensive understanding of the evolving LLZTO surface chemistry during and after these treatments is lacking. Here, glovebox-like H2O and CO2 conditions were recreated in a near ambient pressure X-ray photoelectron spectroscopy chamber to analyze the LLZTO surface under realistic conditions. We find that annealing LLZTO at 600 °C in this atmosphere effectively removes the surface contaminants, but a significant level of contamination reappears upon cooling down. In contrast, HCl(aq) acid etching demonstrates superior Li2CO3 removal and stable surface chemistry post treatment. To avoid air exposure during the acid treatment, an anhydrous HCl solution in diethyl ether was used directly within the glovebox. This novel acid etching strategy delivers the lowest lithium/LLZTO interfacial resistance and the highest critical current density.

Engineering Solution-Processed Non-Crystalline Solid Electrolytes for Li Metal Batteries.

Non-crystalline Li-ion solid electrolytes (SEs), such as lithium phosphorus oxynitride, can uniquely enable high-rate solid-state battery operation over thousands of cycles in thin film form. However, they are typically produced by expensive and low throughput vacuum deposition, limiting their wide application and study. Here, we report non-crystalline SEs of composition Li-Al-P-O (LAPO) with ionic conductivities > 10-7 S cm-1 at room temperature made by spin coating from aqueous solutions and subsequent annealing in air. Homogenous, dense, flat layers can be synthesized with submicrometer thickness at temperatures as low as 230 °C. Control of the composition is shown to significantly affect the ionic conductivity, with increased Li and decreased P content being optimal, while higher annealing temperatures result in decreased ionic conductivity. Activation energy analysis reveals a Li-ion hopping barrier of ≈0.4 eV. Additionally, these SEs exhibit low room temperature electronic conductivity (< 10-11 S cm-1) and a moderate Young's modulus of ≈54 GPa, which may be beneficial in preventing Li dendrite formation. In contact with Li metal, LAPO is found to form a stable but high impedance passivation layer comprised of Al metal, Li-P, and Li-O species. These findings should be of value when engineering non-crystalline SEs for Li-metal batteries with high energy and power densities.

On the Relative Importance of Li Bulk Diffusivity and Interface Morphology in Determining the Stripped Capacity of Metallic Anodes in Solid-State Batteries.

Lithium metal self-diffusion is too slow to sustain large current densities at the interface with a solid electrolyte, and the resulting formation of voids on stripping is a major limiting factor for the power density of solid-state cells. The enhanced morphological stability of some lithium alloy electrodes has prompted questions on the role of lithium diffusivity in these materials. Here, the lithium diffusivity in Li-Mg alloys is investigated by an isotope tracer method, revealing that the presence of magnesium slows down the diffusion of lithium. For large stripping currents the delithiation process is diffusion-limited, hence a lithium metal electrode yields a larger capacity than a Li-Mg electrode. However, at lower currents we explain the apparent contradiction that more lithium can be extracted from Li-Mg electrodes by showing that the alloy can maintain a more geometrically stable diffusion path to the solid electrolyte surface so that the effective lithium diffusivity is improved.