Controlling dendrite propagation in solid-state batteries with engineered stress

Metal dendrite penetration is a mode of electrolyte failure that threatens the viability of metal anode based high energy solid-state batteries. Whether dendrites are driven by mechanical failure or electrochemical degradation of solid electrolytes remains an open question. If internal mechanical forces drive failure, superimposing an external compressive load that counters internal stress may mitigate dendrite penetration. Here, we investigate this hypothesis by dynamically applying mechanical loads to growing lithium metal dendrites in Li6.75La3Zr1.75Ta0.25O12 solid electrolytes. Operando microscopy reveals marked deflection in the dendrite growth trajectory at the onset of compressive loading. At loads near 200 MPa, this deflection is sufficient to avert cell failure. Using fracture mechanics, we quantify the impact of stack pressure and in-plane stresses on dendrite trajectory, chart the residual stresses required to prevent short-circuit failure, and propose cell design approaches to achieve such stresses. The model and experiments show that in the materials studied here, dendrite propagation is dictated by fracture of the electrolyte and that electronic conductivity plays a negligible role

Semi-solid alkali metal electrodes enabling high critical current densities in solid electrolyte batteries

The need for higher energy-density rechargeable batteries has generated interest in alkali metal electrodes paired with solid electrolytes. However, metal penetration and electrolyte fracture at low current densities have emerged as fundamental barriers. Here we show that for pure metals in the Li–Na–K system, the critical current densities scale inversely to mechanical deformation resistance. Furthermore, we demonstrate two electrode architectures in which the presence of a liquid phase enables high current densities while it preserves the shape retention and packaging advantages of solid electrodes. First, biphasic Na–K alloys show K critical current densities (with the K-β″-Al O electrolyte) that exceed 15 mA cm . Second, introducing a wetting interfacial film of Na–K liquid between Li metal and Li La Zr Ta O solid electrolyte doubles the critical current density and permits cycling at areal capacities that exceed 3.5 mAh cm . These design approaches hold promise for overcoming electrochemomechanical stability issues that have heretofore limited the performance of solid-state metal batteries. + ‒2 ‒2 2 3 6.75 3 1.75 0.25 1

Damage relief of ion-irradiated Inconel alloy 718 via annealing

Inconel alloy 718 is a high-strength and corrosion resistant alloy that is commonly used as a beamline vacuum window. The accumulation of irradiation-induced damage substantially decreases the window's service lifetime, and replacing it engenders significant beamline downtime. With this application in mind, herein we examine whether post-irradiation annealing can alleviate irradiation-induced damage of Inconel alloy 718. Inconel alloy 718 was received in a solution annealed state. We then irradiated samples using two different modalities (1.5 MeV H+ and 5 MeV Ni2+) at three representative temperatures for beamline windows (room temperature, 100 degrees C, and 200 degrees C), followed by annealing at temperatures viable for in-situ annealing processes (no anneal, 300 degrees C, and 500 degrees C). Using nanoindentation, we determined that irradiation-induced hardening occurs but is largely mitigated by post-irradiation annealing. Overall, our results suggest that in-situ annealing of radiation damage in Inconel alloy 718 vacuum windows appears feasible, which could potentially decrease beam downtime and maintenance costs

Surgical and procedural skills training at medical school – a national review

AbstractThis national study quantifies procedural and surgical skills training at medical schools in the United Kingdom (UK), a stipulated requirement of all graduates by the General Medical Council (GMC). A questionnaire recorded basic procedural and surgical skills training provided by medical schools and surgical societies in the UK. Skills were extracted from (1) GMC Tomorrows Doctors and (2) The Royal College of Surgeons Intercollegiate Basic Surgical Skills (BSS) course. Data from medical school curricula and extra-curricular student surgical societies were compared against the national GMC guidelines and BSS course content. Data were analysed using Mann–Whitney U tests. Representatives from 23 medical schools completed the survey (71.9% response). Thirty one skills extracted from the BSS course were split into 5 categories, with skills content cross referenced against GMC documentation. Training of surgical skills by medical schools was as follows: Gowning and gloving (72.8%), handling instruments (29.4%), knot tying (17.4%), suturing (24.7%), other surgical techniques (4.3%). Surgical societies provided significantly more training of knot tying (64.4%, P = 0.0013) and suturing (64.5%, P = 0.0325) than medical schools. Medical schools provide minimal basic surgical skills training, partially supplemented by extracurricular student surgical societies. Our findings suggest senior medical students do not possess simple surgical and procedural skills. Newly qualified doctors are at risk of being unable to safely perform practical procedures, contradicting GMC Guidelines. We propose a National Undergraduate Curriculum in Surgery and Surgical Skills to equip newly qualified doctors with basic procedural skills to maximise patient safety