On-Site Fluorination for Enhancing Utilization of Lithium in a Lithium-Sulfur Full Battery

CaF2 nanoparticles enabling LiF-dominated solid electrolyte interphase for dendrite-free and ultra-stable lithium metal batteries

The uncontrollable growth of Li dendrites and severe interfacial parasitic reactions on the Li anode are the primary obstacles to the practical application of lithium (Li) metal batteries. Effective artificial solid electrolyte interphase is capable of regulating uniform Li deposition and isolateing Li from electrolyte, thereby eliminating parasitic reactions. Herein, we rationally design a uniform LiF-dominated solid electrolyte interphase through an in-situ reaction between CaF2 nanoparticles and the Li anode, which allows dendrite-free Li deposition and restrains interfacial deterioration. Accordingly, the protective Li electrode demonstrated exceptional stability, sustaining over 6000 h at a current density of 2 mA cm-2 in symmetric cells and attaining over 1000 cycles with a low capacity decay rate of 0.015 % per cycle in coupling with LiFePO4 cathodes.

Semi-Embedded Structured Bi Nanospheres for Boosted Self-Heating-Induced Healing of Li-Dendrites

It is reported that self-heating-induced healing on lithium metal anodes (LMAs) provides a mitigation strategy for suppressing Li dendrites. However, how to boost the self-heating-induced healing of Li-dendrites and incorporate it into Li-host design remains an imminent problem that needs to be solved. Herein, a new bismuth nanosphere semi-buried carbon cloth (Bi-NS-CC) material with a 3D flexible host structure is proposed. The ultrasmall Bi nanospheres are uniformly and densely distributed on carbon fiber, providing active sites to form uniform Li3 Bi alloy with molten lithium, thereby guiding the injection of molten metallic lithium into the 3D structure to form a self-supporting composite LMAs. The ingenious semi-embedded structure with strong interfacial C─Bi ensures superior mechanical properties. Interestingly, when the current density reaches up to 10 mA cm-2 , the lithium dendrites undergo self-heating. Carbon cloth as a host can quickly and uniformly transfer heat, which induces the uniform migration of Li on anodes. The semi-embedded structure with strong C─Bi ensures Bi nanospheres guide the formation of smooth morphology even under these harsh conditions (high-temperature, high-rate, etc.). Consequently, at 10 mA cm-2 /10 mAh cm-2 , the Li/Li3 Bi-NS-CC realizes ultra-long cycles of 1500 h and ultra-low overpotential of 15 mV in a symmetric cell.

A Bifunctional Fluorine-Free Electrolyte Additive for Realizing Dendrite-Free Lithium Anodes

Owing to the strong energy advantage of lithium anodes, the development of lithium-metal batteries has become an inevitable trend. However, plagued by the instability of solid-electrolyte interphase (SEI) films, lithium metal anodes face challenges such as lithium dendrite formation and volume expansion. Studies have proven that modulating the composition and structure of SEI films by using electrolyte additives is a convenient and valid method. Currently, it is widely accepted that fluoride is an effective additive but, based on the high cost of fluoride production and environmental concerns, the development of fluoride-free additives is of great significance. In this work, the bifunctional additive N,O-bis(trimethylsilyl)acetamide (BSA) is proposed, which can build up a SEI layer that is rich in SiO_x and Li₃ N on the surface of the lithium anode to control the deposition behavior of lithium and clean the electrolyte of HF to protect the electrode. The experimental results indicate that BSA suppresses the generation of lithium dendrites and controls the volume expansion of lithium anodes. Moreover, compared with the commonly used carbonate electrolytes, the battery containing BSA has the best overall performance. Methodologically, the results can be extended to other additives containing Si-O functional groups to replace the same type of fluorine-containing additives.

Two steps synthesis of plum-shaped C@Ni/MnO nanofiber heterostructures for trapping and catalyzing polysulfides in lithium-sulfur batteries

Both spherical MnO as adsorbent and Ni nanoparticles as catalyzer, with highly exposed contact surface area in the carbon nanofibers, are successfully synthesized via electrospinning technology combined with carbothermal reduction. Compared with typical electrospun carbon nanofiber composites, the as-prepared C@Ni/MnO composite fibers as interlayer enable MnO and Ni to contact fully with polysulfides rather than provide local contact surface. With the sulfur loading of 1.6 mg cm^-2 and the approximately 0.1 g composite fibers as interlayer, the cathode shows initial capacity of 687.36 mAh g^-1 at 0.5C and superior capacity retention of 70%. This simple technical route leads a way to prepare nanoparticles with highly exposed contact surfaces partially embedded in the carbon nanofibers, which can be applied in electrocatalysis.