Electrochemically and Thermally Stable Inorganics-Rich Solid Electrolyte Interphase for Robust Lithium Metal Batteries.

Severe dendrite growth and high-level activity of the lithium metal anode lead to a short life span and poor safety, seriously hindering the practical applications of lithium metal batteries. With a trisalt electrolyte design, an F-/N-containing inorganics-rich solid electrolyte interphase on a lithium anode is constructed, which is electrochemically and thermally stable over long-term cycles and safety abuse conditions. As a result, its Coulombic efficiency can be maintained over 98.98% for 400 cycles. An 85.0% capacity can be retained for coin-type full cells with a 3.14 mAh cm-2 LiNi0.5 Co0.2 Mn0.3 O2 cathode after 200 cycles and 1.0 Ah pouch-type full cells with a 4.0 mAh cm-2 cathode after 72 cycles. During the thermal runaway tests of a cycled 1.0 Ah pouch cell, the onset and triggering temperatures were increased from 70.8 °C and 117.4 °C to 100.6 °C and 153.1 °C, respectively, indicating a greatly enhanced safety performance. This work gives novel insights into electrolyte and interface design, potentially paving the way for high-energy-density, long-life-span, and thermally safe lithium metal batteries.

A Solid-State Electrolyte Based on Li0.95 Na0.05 FePO4 for Lithium Metal Batteries.

Solid-state electrolytes (SSEs) play a crucial role in developing lithium metal batteries (LMBs) with high safety and energy density. Exploring SSEs with excellent comprehensive performance is the key to achieving the practical application of LMBs. In this work, the great potential of Li0.95 Na0.05 FePO4 (LNFP) as an ideal SSE due to its enhanced ionic conductivity and reliable stability in contact with lithium metal anode is demonstrated. Moreover, LNFP-based composite solid electrolytes (CSEs) are prepared to further improve electronic insulation and interface stability. The CSE containing 50 wt% of LNFP (LNFP50) shows high ionic conductivity (3.58 × 10-4 S cm-1 at 25 °C) and good compatibility with Li metal anode and cathodes. Surprisingly, the LMB of Li|LNFP50|LiFePO4 cell at 0.5 C current density shows good cycling stability (151.5 mAh g-1 for 500 cycles, 96.5% capacity retention, and 99.3% Coulombic efficiency), and high-energy LMB of Li|LNFP50|Li[Ni0.8 Co0.1 Mn0.1 ]O2 cell maintains 80% capacity retention after 170 cycles, which are better than that with traditional liquid electrolytes (LEs). This investigation offers a new approach to commercializing SSEs with excellent comprehensive performance for high-performance LMBs.

An Anatomy- and Topology-Preserving Framework for Coronary Artery Segmentation.

Coronary artery segmentation is critical for coronary artery disease diagnosis but challenging due to its tortuous course with numerous small branches and inter-subject variations. Most existing studies ignore important anatomical information and vascular topologies, leading to less desirable segmentation performance that usually cannot satisfy clinical demands. To deal with these challenges, in this paper we propose an anatomy- and topology-preserving two-stage framework for coronary artery segmentation. The proposed framework consists of an anatomical dependency encoding (ADE) module and a hierarchical topology learning (HTL) module for coarse-to-fine segmentation, respectively. Specifically, the ADE module segments four heart chambers and aorta, and thus five distance field maps are obtained to encode distance between chamber surfaces and coarsely segmented coronary artery. Meanwhile, ADE also performs coronary artery detection to crop region-of-interest and eliminate foreground-background imbalance. The follow-up HTL module performs fine segmentation by exploiting three hierarchical vascular topologies, i.e., key points, centerlines, and neighbor connectivity using a multi-task learning scheme. In addition, we adopt a bottom-up attention interaction (BAI) module to integrate the feature representations extracted across hierarchical topologies. Extensive experiments on public and in-house datasets show that the proposed framework achieves state-of-the-art performance for coronary artery segmentation.

Versatile Asymmetric Separator with Dendrite-Free Alloy Anode Enables High-Performance Li-S Batteries.

Lithium-sulfur batteries (LSBs) with extremely-high theoretical energy density (2600 Wh kg-1 ) are deemed to be the most likely energy storage system to be commercialized. However, the polysulfides shuttling and lithium (Li) metal anode failure in LSBs limit its further commercialization. Herein, a versatile asymmetric separator and a Li-rich lithium-magnesium (Li-Mg) alloy anode are applied in LSBs. The asymmetric separator is consisted of lithiated-sulfonated porous organic polymer (SPOP-Li) and Li6.75 La3 Zr1.75 Nb0.25 O12 (LLZNO) layers toward the cathode and anode, respectively. SPOP-Li serves as a polysulfides barrier and Li-ion conductor, while the LLZNO functions as an "ion redistributor". Combining with a stable Li-Mg alloy anode, the symmetric cell achieves 5300 h of Li stripping/plating and the modified LSBs exhibit a long lifespan with an ultralow fading rate of 0.03% per cycle for over 1000 cycles at 5 C. Impressively, even under a high-sulfur-loading (6.1 mg cm-2 ), an area capacity of 4.34 mAh cm-2 after 100 cycles can still be maintained, demonstrating high potential for practical application.

Boosting Polysulfide Catalytic Conversion and Facilitating Li+ Transportation by Ion-Selective COFs Composite Nanowire for LiS Batteries.

The large-scale application of lithium-sulfur batteries (LSBs) has been impeded by the shuttle effect of lithium-polysulfides (LiPSs) and sluggish redox kinetics since which lead to irreversible capacity decay and low sulfur utilization. Herein, a hierarchical interlayer constructed by boroxine covalent organic frameworks (COFs) with high Li+ conductivity is fabricated via an in situ polymerization method on carbon nanotubes (CNTs) (C@COF). The as-prepared interlayer delivers a high Li+ ionic conductivity (1.85 mS cm-1 ) and Li+ transference number (0.78), which not only acts as a physical barrier, but also a bidirectional catalyst for LiPSs redox process owing to the abundant heterointerfaces between the inner conductive CNTs and the outer COFs. After coupling such a catalytic interlayer with sulfur cathode, the LSBs exhibit a low decay rate of 0.07% per cycle over 500 cycles at 1 C, and long cycle life at 3 C (over 1000 cycles). More importantly, a remarkable areal capacity of around 4.69 mAh cm-2 can still be maintained after 50 cycles even under a high sulfur loading condition (6.8 mg cm-2 ). This work paves a new way for the design of the interlayer with bidirectional catalytic behavior in LSBs.

Nonporous Gel Electrolytes Enable Long Cycling at High Current Density for Lithium-Metal Anodes.

Lithium-metal anodes with high theoretical capacity and ultralow redox potential are regarded as a "holy grail" of the next-generation energy-storage industry. Nevertheless, Li inevitably reacts with conventional liquid electrolytes, resulting in uneven electrodeposition, unstable solid electrolyte interphase, and Li dendrite formation that all together lead to a decrease in active lithium, poor battery performance, and catastrophic safety hazards. Here, we report a unique nonporous gel polymer electrolyte (NP-GPE) with a uniform and dense structure, exhibiting an excellent combination of mechanical strength, thermal stability, and high ionic conductivity. The nonporous structure contributed to a uniform distribution of lithium ions for dendrite-free lithium deposition, and Li/NP-GPE/Li symmetric cells can maintain an extremely low and stable polarization after cycling at a high current density of 10 mA cm-2. This work provides an insight that the NP-GPE can be considered as a candidate for practical applications for lithium-metal anodes.

Methods to Improve Lithium Metal Anode for Li-S Batteries.

The lithium-sulfur (Li-S) battery has received a lot of attention because it is characterized by high theoretical energy density (2,600 Wh/kg) and low cost. Though many works on the "shuttle effect" of polysulfide have been investigated, lithium metal anode is a more challenging problem, which leads to a short life, low coulombic efficiency, and safety issues related to dendrites. As a result, the amelioration of lithium metal anode is an important means to improve the performance of lithium sulfur battery. In this paper, improvement methods on lithium metal anode for lithium sulfur batteries, including adding electrolyte additives, using solid, and/or gel polymer electrolyte, modifying separators, applying a protective coating, and providing host materials for lithium deposition, are mainly reviewed. In addition, some challenging problems, and further promising directions are also pointed out for future research and development of lithium metal for Li-S batteries.