Assessing Long-Term Cycling Stability of Single-Crystal Versus Polycrystalline Nickel-Rich NCM in Pouch Cells with 6 mAh cm-2 Electrodes.

Lithium-ion batteries based on single-crystal LiNi1- x - y Cox Mny O2 (NCM, 1-x-y ≥ 0.6) cathode materials are gaining increasing attention due to their improved structural stability resulting in superior cycle life compared to batteries based on polycrystalline NCM. However, an in-depth understanding of the less pronounced degradation mechanism of single-crystal NCM is still lacking. Here, a detailed postmortem study is presented, comparing pouch cells with single-crystal versus polycrystalline LiNi0.60 Co0.20 Mn0.20 O2 (NCM622) cathodes after 1375 dis-/charge cycles against graphite anodes. The thickness of the cation-disordered layer forming in the near-surface region of the cathode particles does not differ significantly between single-crystal and polycrystalline particles, while cracking is pronounced for polycrystalline particles, but practically absent for single-crystal particles. Transition metal dissolution as quantified by time-of-flight mass spectrometry on the surface of the cycled graphite anode is much reduced for single-crystal NCM622. Similarly, CO2 gas evolution during the first two cycles as quantified by electrochemical mass spectrometry is much reduced for single-crystal NCM622. Benefitting from these advantages, graphite/single-crystal NMC622 pouch cells are demonstrated with a cathode areal capacity of 6 mAh cm-2 with an excellent capacity retention of 83% after 3000 cycles to 4.2 V, emphasizing the potential of single-crystalline NCM622 as cathode material for next-generation lithium-ion batteries.

Epitaxial Thin Films as a Model System for Li-Ion Conductivity in Li4Ti5O12.

Using an epitaxial thin-film model system deposited by pulsed laser deposition (PLD), we study the Li-ion conductivity in Li4Ti5O12, a common anode material for Li-ion batteries. Epitaxy, phase purity, and film composition across the film thickness are verified employing out-of-plane and in-plane X-ray diffraction, transmission electron microscopy, time-of-flight mass spectrometry, and elastic recoil detection analysis. We find that epitaxial Li4Ti5O12 behaves like an ideal ionic conductor that is well described by a parallel RC equivalent circuit, with an ionic conductivity of 2.5 × 10-5 S/cm at 230 °C and an activation energy of 0.79 eV in the measured temperature range of 205 to 350 °C. Differently, in a co-deposited polycrystalline Li4Ti5O12 thin film with an average in-plane grain size of <10 nm, a more complex behavior with contributions from two distinct processes is observed. Ultimately, epitaxial Li4Ti5O12 thin films can be grown by PLD and reveal suitable transport properties for further implementation as zero-strain and grain boundary free anodes in future solid-state microbattery designs.

The pathologic basis of recovery.

More patients with end-stage heart failure are now being supported by left ventricular assist devices (LVAD) as a bridge to heart transplant. The LVAD unloads the failing heart and modifies the myocardial structure, with regression of left ventricular hypertrophy. The regression of hypertrophy has been reported histomorphologically in paired samples of myocardial tissues obtained from the same patient at the time of LVAD implantation and the heart excised at transplant. The understanding of the mechanisms of recovery may contribute to strategic development for LVAD weaning and the use of LVAD as a destination therapy.

Initial results of clinical trial with a new left ventricular assist device (LVAD) providing synchronous pulsatile flow.

OBJECTIVES: A multicentric European Clinical Study is ongoing to evaluate safety and efficacy of a new pulsatile implantable LVAD (BestBeat), smaller and lighter than similar devices, capable of providing synchronous and counterpulsating flow with respect to the LV of end-stage heart failure patients. Preliminary clinical results are reported. METHODS: The new BestBeat LVAD was used, consisting of an implantable pulsatile blood pump, electromechanically driven by a ball screw mechanism, and a wearable electronic controller and power sources. The clinical trial was conducted at 5 european centers. Adult patients affected by CHF in NYHA Class IV despite optimized medical treatment were enrolled. The primary study endpoint was survival at 90 days. Further study endpoints were maintenance of adequate LVAD pump flow and a minimum rate of adverse events during support. RESULTS: As of June 2008, 6 patients received the implant. Cumulative support time was 3.7 years, median support time 176 days. All patients who completed the study survived except for one, who died after 48 days, due to combined infection and cerebrovascular accident. Another two patients died: one from intracranial bleeding 113 days after implant, and one from septic shock after 123 days. Hemodynamic improvement with CI>2.0 l/min/m2 and recovery of end-organ function expressed by consistent improvement of BUN, creatinine and bilirubin were reached in all patients. No device failure was observed. There was no bleeding requiring re-exploration, no hemolysis and only two device-related infections (both in one patient). Neurologic events were reported, the most serious ones occurring in patients with pre-implant respiratory and kidney failure. Three patients were discharged home. Two patients were successfully transplanted, one after 6 months and one after 13 months on device. CONCLUSIONS: Good performance and efficacy of the device were observed; the endpoints of the study were achieved, and its safety was consistent with expectations. The ongoing study will allow further conclusions to be drawn.

Minimally invasive approach for complex cardiac surgery procedures.

BACKGROUND: A minimally invasive approach through an upper ministernotomy (UMS) has been used in our Division since 1997. On the basis of favorable outcome we have gradually extended this approach from isolated aortic valve replacement (AVR) to more complex cardiac surgery procedures and it is currently our first choice for a variety of procedures. Here we report our 11 years experience. METHODS: From 1997 to December 2007, 1,126 procedures were performed at our department, using UMS. Isolated procedures on the aortic valve were performed in 695 patients (61%). Isolated procedures on the aortic valve as redo operation were performed in 77 patients (7%). Complex cardiac surgery procedures (including double valve replacement-repair, ascending aorta-aortic arch replacement, aortic root replacement, aortic dissection, AVR combined with coronary surgery, and complex redo procedures) were performed in 354 patients (32%). Early postoperative outcome was evaluated considering three different groups according to the surgical procedure (first time AVR, redo AVR, and complex procedure). RESULTS: Overall conversion to full sternotomy was required in 16 patients (1.4%) with no significant differences between isolated AVR (9 patients, 1.3%) and complex or redo procedures (1 patient [1.2%] and 6 patients [1.6%], respectively). Forty-seven patients died in hospital (cumulative in-hospital mortality of 4.1 %). Mortality according to the procedure was 6.7, 3.8, and 2.8% for complex, redo AVR, or isolated AVR procedures, respectively, with a significant difference only for the complex procedures. Similarly, early postoperative outcome in terms of incidence of prolonged mechanical ventilation and ICU stay was significantly different only in the complex procedure group. Incidence of surgical revision (5.1, 2.9, and 2.7% for complex, redo, or isolated AVR procedures, respectively) showed no statistically significant differences regardless the type of procedures. CONCLUSIONS: Our experience clearly shows that a minimally invasive approach through upper ministernotomy is feasible and safe not only for isolated AVR but that it can also be utilized for a variety of complex surgical procedures. Minimizing surgical access may be helpful in patients undergoing complex surgical procedures, especially redo procedures, without compromising the surgical result.

Arrow CorAide left ventricular assist system: initial experience of the cardio-thoracic surgery center in Pavia.

PURPOSE: The aim of the present study is to describe our preliminary experience with the Arrow CorAide left ventricular assist system (LVAS). DESCRIPTION: The Arrow CorAide LVAS is a small implantable, continuous flow centrifugal pump, with a fully suspended rotating assembly, intended as a bridge to transplant device, bridge to recovery, and for long-term use. EVALUATION: Since April 2005 we have implanted the CorAide LVAS in 2 male patients, with a patient follow-up of more than 6 months. Surgical procedures were uneventful, and both patients had an uneventful postoperative course, with fast weaning from mechanical ventilation and inotropic support. No thromboembolic events, infective complication, hemolysis, or mechanical failure occurred. To date, both patients are in New York Heart Association class I. CONCLUSIONS: In our initial experience the CorAide LVAS blood pump is nonthrombogenic, nonhemolytic, and easy to implant. Both patients have improved their functional status. Further follow-up is needed to assess long-term results.