Strategies towards enabling lithium metal in batteries: interphases and electrodes

Despite the continuous increase in capacity, lithium-ion intercalation batteries are approaching their performance limits. As a result, research is intensifying on next-generation battery technologies. The use of a lithium metal anode promises the highest theoretical energy density and enables use of lithium-free or novel high-energy cathodes. However, the lithium metal anode suffers from poor morphological stability and Coulombic efficiency during cycling, especially in liquid electrolytes. In contrast to solid electrolytes, liquid electrolytes have the advantage of high ionic conductivity and good wetting of the anode, despite the lithium metal volume change during cycling. Rapid capacity fade due to inhomogeneous deposition and dissolution of lithium is the main hindrance to the successful utilization of the lithium metal anode in combination with liquid electrolytes. In this perspective, we discuss how experimental and theoretical insights can provide possible pathways for reversible cycling of twodimensional lithium metal. Therefore, we discuss improvements in the understanding of lithium metal nucleation, deposition, and stripping on the nanoscale. As the solid–electrolyte interphase (SEI) plays a key role in the lithium morphology, we discuss how the proper SEI design might allow stable cycling. We highlight recent advances in conventional and (localized) highly concentrated electrolytes in view of their respective SEIs. We also discuss artificial interphases and three-dimensional host frameworks, which show prospects of mitigating morphological instabilities and suppressing large shape change on the electrode level

Mortality from gastrointestinal congenital anomalies at 264 hospitals in 74 low-income, middle-income, and high-income countries: a multicentre, international, prospective cohort study

Summary Background Congenital anomalies are the fifth leading cause of mortality in children younger than 5 years globally. Many gastrointestinal congenital anomalies are fatal without timely access to neonatal surgical care, but few studies have been done on these conditions in low-income and middle-income countries (LMICs). We compared outcomes of the seven most common gastrointestinal congenital anomalies in low-income, middle-income, and high-income countries globally, and identified factors associated with mortality. Methods We did a multicentre, international prospective cohort study of patients younger than 16 years, presenting to hospital for the first time with oesophageal atresia, congenital diaphragmatic hernia, intestinal atresia, gastroschisis, exomphalos, anorectal malformation, and Hirschsprung’s disease. Recruitment was of consecutive patients for a minimum of 1 month between October, 2018, and April, 2019. We collected data on patient demographics, clinical status, interventions, and outcomes using the REDCap platform. Patients were followed up for 30 days after primary intervention, or 30 days after admission if they did not receive an intervention. The primary outcome was all-cause, in-hospital mortality for all conditions combined and each condition individually, stratified by country income status. We did a complete case analysis. Findings We included 3849 patients with 3975 study conditions (560 with oesophageal atresia, 448 with congenital diaphragmatic hernia, 681 with intestinal atresia, 453 with gastroschisis, 325 with exomphalos, 991 with anorectal malformation, and 517 with Hirschsprung’s disease) from 264 hospitals (89 in high-income countries, 166 in middleincome countries, and nine in low-income countries) in 74 countries. Of the 3849 patients, 2231 (58·0%) were male. Median gestational age at birth was 38 weeks (IQR 36–39) and median bodyweight at presentation was 2·8 kg (2·3–3·3). Mortality among all patients was 37 (39·8%) of 93 in low-income countries, 583 (20·4%) of 2860 in middle-income countries, and 50 (5·6%) of 896 in high-income countries (p<0·0001 between all country income groups). Gastroschisis had the greatest difference in mortality between country income strata (nine [90·0%] of ten in lowincome countries, 97 [31·9%] of 304 in middle-income countries, and two [1·4%] of 139 in high-income countries; p≤0·0001 between all country income groups). Factors significantly associated with higher mortality for all patients combined included country income status (low-income vs high-income countries, risk ratio 2·78 [95% CI 1·88–4·11], p<0·0001; middle-income vs high-income countries, 2·11 [1·59–2·79], p<0·0001), sepsis at presentation (1·20 [1·04–1·40], p=0·016), higher American Society of Anesthesiologists (ASA) score at primary intervention (ASA 4–5 vs ASA 1–2, 1·82 [1·40–2·35], p<0·0001; ASA 3 vs ASA 1–2, 1·58, [1·30–1·92], p<0·0001]), surgical safety checklist not used (1·39 [1·02–1·90], p=0·035), and ventilation or parenteral nutrition unavailable when needed (ventilation 1·96, [1·41–2·71], p=0·0001; parenteral nutrition 1·35, [1·05–1·74], p=0·018). Administration of parenteral nutrition (0·61, [0·47–0·79], p=0·0002) and use of a peripherally inserted central catheter (0·65 [0·50–0·86], p=0·0024) or percutaneous central line (0·69 [0·48–1·00], p=0·049) were associated with lower mortality. Interpretation Unacceptable differences in mortality exist for gastrointestinal congenital anomalies between lowincome, middle-income, and high-income countries. Improving access to quality neonatal surgical care in LMICs will be vital to achieve Sustainable Development Goal 3.2 of ending preventable deaths in neonates and children younger than 5 years by 2030

Solid Electrolyte Formation in LI-Metal Batteries and LIFSI/TMP Electrolyte

Rechargeable Li-ion batteries (LIB) are the most popular devices for energy storage but still a lot of research needs to be done to improve their cycling and storage capacity. LIB feature energies densities in the range of 100-265 Wh/kg which is very low if compared with gasoline in which the range is in the order of 12,000 Wh/kg. Therefore, Li-metal has been proposed as an anode material because the energy density of the battery could increase up to 2,600 Wh/kg for a Li-Sulfur battery and to 3,458 Wh/kg for a Li-air (O₂) battery. With the addition of Li-metal as an anode material a new set of batteries called lithium metal batteries (LMB) can be developed with the potential to increase the cell-level energy of the LIBs. Therefore, focus is needed on the lithiation process of Li-metal anodes where it is known the mechanical, electrochemical, and electric phenomena such as cracking, SEI formation and ionic-clustering, respectively, that occur during the charge/discharge cycles. Performing molecular dynamics simulations of an electrolyte comprising trimethyl phosphate (TMP) solvent and a lithium bis(fluorosulfonyl)imide (LiFSI) salt, the effects of salt concentration on solvation and ion-transport are explored. Three LiFSI-TMP electrolyte salt concentrations of 0.7, 1.43 and 3.82 molar are simulated. A statistical analysis was performed to study ion-pairing, clustering, diffusivity, conductivity, and coordination of Li-ions, providing insights into relations between molecular structures and transport properties. Molecular structure of ionic components changes as concentration increases, from a predominant solvent separated ion pair (SSIP) and contact ion pair (CIP) to aggregate (AGG) salt and ionic cluster formation. The formation of ionic clusters suggests that the diffusion mechanism of Li-ions changes from a hopping/exchange to a vehicular mechanism as concentration increases; this is validated by a decrease of ionic conductivity. Ionicity was also calculated to reveal how the ionic motion changes from an uncorrelated to a correlated one as the salt concentration increases. Identifying the mechanism of SEI formation at electronic and atomic levels is especially important to understand how the SEI formation affects the overall battery performance such as the decrease of active material, decrease of cell potential, and interfacial stability. Ab initio molecular dynamics simulations were performed for Li⁺-conducting electrolytes based on trimethyl phosphates (TMP) and lithium bis(fluorosulfonyl)imide (Li⁺FSI⁻) salt in contact with a Li-metal electrode. We focused on the transient-state behavior at the electrolyte, interfacial electrolyte−Li-metal electrode, and lithium reference electrode−electrolyte−Li-metal electrode to study dynamics and activation energy barriers of the Li⁺ ion, electrochemical and thermal stability of the interface electrode−electrolyte, and potential behavior of the Li-metal electrode, respectively. An interfacial study is performed using ab initio molecular dynamics simulations to elucidate the solid electrolyte interphase (SEI) evolution formed between an electrolyte based on trimethyl phosphates (TMP) and lithium bis(fluorosulfonyl)imide(Li⁺FSI⁻) salt in contact with a Li-metal electrode. Going beyond the initial SEI composition generated due to the degradation of one counter-ion adding a second and third counter-ions ana analysis of how the initial SEI evolution is performed. The results indicate a different product formation due to the LiFSI salt dissociation as the SEI is formed. The products formed due to the dissociation of the 1st LiFSI salt when in direct contact with the Li-metal anode are Li₂O, Li₂S, Li₃N and LiF. These four Li-binary products compose the formed SEI. Then, a 2nd LiFSI is located at the electrolyte/SEI/Li-metal. The products formed due to the dissociation of the 2nd LiFSI when in contact with the SEI are Li2S, Li₂O, LiF, Li₃NSO₂. Finally, a 3rd LiFSI is located at the electrolyte/SEI/Li-metal. The products formed due to the dissociation of the 3rd LiFSI when in contact with the SEI are Li₂SO₂NSO₂ and LiF. Computational techniques such as molecular dynamics (MD) simulations can simulate a large number of atoms, in the order of 10⁵ interacting through their forcefields. A nanobattery MD model is an accurate, yet simple model to study electrochemical phenomena occurring in in any rechargeable battery. A regression machine learning algorithm is proposed to overpass paramount timescale limitations of any atomistic MD model. The primary limitation of the nanobattery model is the extremely short charging time compared to the longer charging time in a real battery. Using data from several macro-scale commercial Li-ion batteries, and a nanobattery MD model, we constructed a scaling regression algorithm to scale the values obtained from the nanobattery MD model to a macro-scale Li-ion battery. The goal is to demonstrate that three transport properties: 1) the time, tLi, a Li-ion spend to travel from cathode to anode; 2) the superficial density frequency of arrival Li-ions, ALi (s⁻¹A⁻²); and 3) the frequency, fLi, of Li ions arrival to the anode, can be incorporated in one model that could predict the macro-scale variables having as an input the nano-scale variables

Direct in situ measurements of electrical properties of solid–electrolyte interphase on lithium metal anodes

The solid–electrolyte interphase (SEI) critically governs the performance of rechargeable batteries. An ideal SEI is expected to be electrically insulative to prevent persistently parasitic reactions between the electrode and the electrolyte and ionically conductive to facilitate Faradaic reactions of the electrode. However, the true nature of the electrical properties of the SEI remains hitherto unclear due to the lack of a direct characterization method. Here we use in situ bias transmission electron microscopy to directly measure the electrical properties of SEIs formed on copper and lithium substrates. We reveal that SEIs show a voltage-dependent differential conductance. A higher rate of differential conductance induces a thicker SEI with an intricate topographic feature, leading to an inferior Coulombic efficiency and cycling stability in Li||Cu and Li||LiNi0.8Mn0.1Co0.1O2 cells. Our work provides insight into the targeted design of the SEI with desired characteristics towards better battery performance

Timing of nasogastric tube insertion and the risk of postoperative pneumonia: an international, prospective cohort study

Aim: Aspiration is a common cause of pneumonia in patients with postoperative ileus. Insertion of a nasogastric tube (NGT) is often performed, but this can be distressing. The aim of this study was to determine whether the timing of NGT insertion after surgery (before versus after vomiting) was associated with reduced rates of pneumonia in patients undergoing elective colorectal surgery. Method: This was a preplanned secondary analysis of a multicentre, prospective cohort study. Patients undergoing elective colorectal surgery between January 2018 and April 2018 were eligible. Those receiving a NGT were divided into three groups, based on the timing of the insertion: routine NGT (inserted at the time of surgery), prophylactic NGT (inserted after surgery but before vomiting) and reactive NGT (inserted after surgery and after vomiting). The primary outcome was the development of pneumonia within 30&nbsp;days of surgery, which was compared between the prophylactic and reactive NGT groups using multivariable regression analysis. Results: A total of 4715 patients were included in the analysis and 1536 (32.6%) received a NGT. These were classified as routine in 926 (60.3%), reactive in 461 (30.0%) and prophylactic in 149 (9.7%). Two hundred patients (4.2%) developed pneumonia (no NGT 2.7%; routine NGT 5.2%; reactive NGT 10.6%; prophylactic NGT 11.4%). After adjustment for confounding factors, no significant difference in pneumonia rates was detected between the prophylactic and reactive NGT groups (odds ratio 1.03, 95% CI 0.56\u20131.87, P&nbsp;=&nbsp;0.932). Conclusion: In patients who required the insertion of a NGT after surgery, prophylactic insertion was not associated with fewer cases of pneumonia within 30&nbsp;days of surgery compared with reactive insertion