Reduced graphene oxide-encaged submicron-silicon anode interfacially stabilized by Al2O3 nanoparticles for efficient lithium-ion batteries.

Silicon-carbon composites have been recognized as some of the most promising anode candidates for advancing new-generation lithium-ion batteries (LIBs). The development of high-efficiency silicon/graphene anodes through a simple and cost-effective preparation route is significant. Herein, by using micron silicon as raw material, we designed a mesoporous composite of silicon/alumina/reduced graphene oxide (Si/Al2O3/RGO) via a two-step ball milling combined annealing process. Commercial Al2O3 nanoparticles are introduced as an interlayer due to the toughening effect, while RGO nanosheets serve as a conductive and elastic coating to protect active submicron silicon particles during lithium alloying/dealloying reactions. Owing to the rational porous structure and dual protection strategy, the core/shell structured Si/Al2O3/RGO composite is efficient for Li+ storage and demonstrates improved electrical conductivity, accelerated charge transfer and electrolyte diffusion, and especially high structural stability upon charge/discharge cycling. As a consequence, Si/Al2O3/RGO yields a high discharge capacity of 852 mA h g-1 under a current density of 500 mA g-1 even after 200 cycles, exhibiting a high capacity retention of ∼85%. Besides, Si/Al2O3/RGO achieves excellent cycling reversibility and superb high-rate capability with a stable specific capacity of 405 mA h g-1 at 3000 mA g-1. Results demonstrate that the Al2O3 interlayer is synergistic with the indispensable RGO nanosheet shells, affording more buffer space for silicon cores to alleviate the mechanical expansion and thus stabilizing active silicon species during charge/discharge cycles. This work provides an alternative low-cost approach to achieving high-capacity silicon/carbon composites for high-performance LIBs.

Impact of permissive hypercapnia on regional cerebral oxygen saturation and postoperative cognitive function in patients undergoing cardiac valve replacement.

BACKGROUND: Cardiac valve replacement (CVR) is currently the main surgical treatment for patients with valvular heart diseases (VHD). Postoperative cognitive dysfunction (POCD) is one of the most serious complications of cardiac surgery. Permissive hypercapnia (PHC), an important lung-protective ventilation strategy, has protective effects on vital organs, including the heart, lungs, and central nervous system (CNS). The main objective of this study is to assess the effect of the PHC ventilation strategy on rSO2 and postoperative cognitive function in patients undergoing CVR. METHODS: A total of 66 patients undergoing CVR were included and randomly divided into the PHC ventilation group (Group H, n=33) and conventional ventilation group (Group C, n=33). Patients of both groups were subjected to conventional ventilation before cardiopulmonary bypass (CPB). patients in Group H were subjected to the PHC ventilation strategy to keep the partial pressure of carbon dioxide (PaCO2) at 46-60 mmHg. RESULTS: (I) Group H had a lower HR at T0 and T1 (P<0.05) and higher CO at T3 and T4 (P<0.05) than Group C. (II) Group H had higher rSO2 at T4 (P<0.05), lower pH and lactate (Lac) at T4 (P<0.05), higher PaCO2 at T3 and T4 (P<0.05), and lower PaO2 at T3 and T4 (P<0.05). (III) Compared to 1 d before surgery, the MMSE scores of both groups were lower 24 h after surgery (P<0.05). CONCLUSIONS: PHC can increase the rSO2 of patients undergoing CVR, increase cerebral blood flow, improve the cerebral oxygen supply/consumption balance, and play a protective role in the brain. It has no significant impact on the incidence of POCD.