Lithium (Li) metal is an ideal anode material for rechargeable batteries due to its extremely high theoretical specific capacity (3860 mA h g À1 ), low density (0.59 g cm À3 ) and the lowest negative electrochemical potential (À3.040 V vs. the standard hydrogen electrode). Unfortunately, uncontrollable dendritic Li growth and limited Coulombic efficiency during Li deposition/stripping inherent in these batteries have prevented their practical applications over the past 40 years. With the emergence of post-Li-ion batteries, safe and efficient operation of Li metal anodes has become an enabling technology which may determine the fate of several promising candidates for the next generation energy storage systems, including rechargeable Li-air batteries, Li-S batteries, and Li metal batteries which utilize intercalation compounds as cathodes. In this paper, various factors that affect the morphology and Coulombic efficiency of Li metal anodes have been analyzed. Technologies utilized to characterize the morphology of Li deposition and the results obtained by modelling of Li dendrite growth have also been reviewed.Finally, recent development and urgent need in this field are discussed.

As lung ultrasound (LUS) is a noninvasive, radiation-free, repeatable and portable imaging tool suitable for a point-of-care use, several recent literature reports have emphasized its role as the ideal screening tool for SARS-CoV2 pneumonia. To evaluate the actual diagnostic accuracy of LUS for this purpose, we performed a systematic comparative study between LUS and CT scan ndings in a population of 82 patients hospitalized because of COVID-19. LUS and Chest CT have been performed in all patients within 6-12 hours from the admission. The sensitivity of LUS in assessing typical CT ndings was 60%. Despite LUS detected consolidations adherent to pleural surface in all cases, it was not able to detect all the consolidations assessed at CT scan (p=0.002), showing a risk to underestimate the actual disease's extent. Moreover, only 70% of pleural surface is visible by LUS. Considering that the speci city and the positive predictive value of the same LUS signs may be lowered in a normal setting of non epidemic COVID-19 and in case of pre-existing cardio-pulmonary diseases, LUS use should not be indicated for diagnosis of COVID-19. However, it may be very useful for the assessment of pleural effusion and to guide safer uid drainage.

Over the past few years, in situ transmission electron microscopy (TEM) studies of lithium ion batteries using an open-cell configuration have helped us to gain fundamental insights into the structural and chemical evolution of the electrode materials in real time. In the standard open-cell configuration, the electrolyte is either solid lithium oxide or an ionic liquid, which is point-contacted with the electrode. This cell design is inherently different from a real battery, where liquid electrolyte forms conformal contact with electrode materials. The knowledge learnt from open cells can deviate significantly from the real battery, calling for operando TEM technique with conformal liquid electrolyte contact. In this paper, we developed an operando TEM electrochemical liquid cell to meet this need, providing the configuration of a real battery and in a relevant liquid electrolyte. To demonstrate this novel technique, we studied the lithiation/delithiation behavior of single Si nanowires. Some of lithiation/delithation behaviors of Si obtained using the liquid cell are consistent with the results from the open-cell studies. However, we also discovered new insights different from the open cell configuration-the dynamics of the electrolyte and, potentially, a future quantitative characterization of the solid electrolyte interphase layer formation and structural and chemical evolution.

No abstract

Suppressing lithium (Li) dendrite growth is one of the most critical challenges for the development of Li metal batteries. Here, we report for the first time the growth of dendrite-free lithium films with a self-aligned and highly compacted nanorod structure when the film was deposited in the electrolyte consisting of 1.0 M LiPF6 in propylene carbonate with 0.05 M CsPF6 as an additive. Evolution of both the surface and the cross-sectional morphologies of the Li films during repeated Li deposition/stripping processes were systematically investigated. It is found that the formation of the compact Li nanorod structure is preceded by a solid electrolyte interphase (SEI) layer formed on the surface of the substrate. Electrochemical analysis indicates that an initial reduction process occurred at ∼ 2.05 V vs Li/Li(+) before Li deposition is responsible for the formation of the initial SEI, while the X-ray photoelectron spectroscopy indicates that the presence of CsPF6 additive can largely enhance the formation of LiF in this initial SEI. Hence, the smooth Li deposition in Cs(+)-containing electrolyte is the result of a synergistic effect of Cs(+) additive and preformed SEI layer. A fundamental understanding on the composition, internal structure, and evolution of Li metal films may lead to new approaches to stabilize the long-term cycling stability of Li metal and other metal anodes for energy storage applications.

The application of lithium (Li) metal anodes in rechargeable batteries is hindered by Li dendrite growth during Li deposition and low Li Coulombic efficiency (CE), where the nonaqueous electrolyte plays a critical role. In this work, the effects of different carbonate solvents and Li salts on Li deposition morphology and CE were systematically investigated. Typically, cyclic carbonates favor the formation of uniform Li films and improve Li CE more than linear carbonates do. Several specific cyclic carbonates that are conventionally used as solid electrolyte interphase (SEI) formation additives in Li-ion batteries can also improve the CE of Li anodes. Furthermore, among the nine electrolyte salts studied, LiAsF6 and lithium bis(oxalato)borate (LiBOB) lead to the highest CE. LiBOB also leads to better uniformity of deposited Li than other salts do. Considering the better safety of LiBOB as compared to LiAsF6, LiBOB is a promising salt for rechargeable Li metal batteries with high CE. By combining the best electrolyte solvent/salt that can lead to high CE with novel electrolyte additives that can prevent dendrite formation, it is possible to find an electrolyte that not only prevents Li dendrite formation but also leads to high CE during Li deposition/stripping processes.

Development of novel electrolytes with increased electrochemical stability is critical for the next generation battery technologies. In situ electrochemical fluid cells provide the ability to rapidly and directly characterize electrode/electrolyte interfacial reactions under conditions directly relevant to the operation of practical batteries. In this paper, we have studied the breakdown of a range of inorganic/salt complexes relevant to state-of-the-art Li-ion battery systems by in situ (scanning) transmission electron microscopy ((S)TEM). In these experiments, the electron beam itself caused the localized electrochemical reaction that allowed us to observe electrolyte breakdown in real-time. The results of the in situ (S)TEM experiments matches with previous stability tests performed during battery operation and the breakdown products and mechanisms are also consistent with known mechanisms. This analysis indicates that in situ liquid stage (S)TEM observations could be used to directly test new electrolyte designs and identify a smaller library of candidate solutions deserving of more detailed characterization. A systematic study of electrolyte degradation is also a necessary first step for any future controlled in operando liquid (S)TEM experiments intent on visualizing working batteries at the nanoscale.

Spatial and morphology control over lithium (Li) metal nucleation and growth, as well as improving Li Coulombic efficiency (CE), are among the most challenging issues for rechargeable Li metal batteries. Here, we report that LiAsF6 and cyclic carbonate additives such as vinylene carbonate (VC) or fluoroethylene carbonate (FEC) can work synergistically to address these challenges. It is revealed that LiAsF6 can be reduced to Li x As alloy and LiF, which act as nanosized seeds for Li growth and form a robust solid electrolyte interface layer. The addition of VC or FEC not only enables the uniform distribution of Li x As seeds but also improves the flexibility of the solid electrolyte interface layer. As a result, highly compact, uniform, and dendrite-free Li film with vertically aligned column structure can be obtained with increased Li CE, and the Li metal batteries using the electrolyte with both LiAsF6 and cyclic carbonate additives can have improved cycle life.