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Metal fluorides (MFs) are regarded as high‐capacity conversion cathode materials for next‐generation lithium‐ion batteries with high energy density. However, these cathodes suffer from poor electronic conductivity, sluggish reaction kinetics, and deleterious cathode solid electrolyte interface (CEI) formation, which may cause rapid cell degradation upon cycling. Herein, a low temperature chemical vapor deposition (CVD) carbon coating technology is successfully achieved to coat MFs‐FeF2 with a thin amorphous carbon layer, which promotes the formation of a stable CEI with improved electronic and ionic transport property. Consequently, a discharge capacity higher than 450 mAh g−1 of the CVD coated FeF2 is achieved with a capacity retention at about 75% after 2500 cycles in a saturated electrolyte. Moreover, an unprecedented cycling performance with the discharge capacity of 350 mAh g−1 after 500 cycles in a super diluted electrolyte is also achieved. Advanced cryo‐electron microscopy reveals that the carbon coating significantly suppresses the undesirable CEI formation and promotes the formation of a thin CEI with excellent chemo‐mechanical property. This work provides a feasible technology to stabilize the important interface on MFs and offers a new strategy to accelerate the commercial adoption of such cathodes. [ABSTRACT FROM AUTHOR]

Concentration of electrolyte has significant effects on performances of rechargeable batteries. Previous studies mainly focused on concentrated electrolytes. So far, only several recipes on low‐concentration electrolytes were studied, performing enhanced performance in advanced rechargeable batteries. Here, based on common electrolyte components, a low‐concentration electrolyte composed of 0.2 M lithium hexafluorophosphate (LiPF6) solvated in fluoroethylene carbonate (FEC) and ethyl methyl carbonate (EMC) is employed for high‐voltage Li metal battery. The synergistic working mechanisms of introducing fluorine‐containing solvent in the solvated structure and low salt concentration effect are revealed, resulting in LiF‐rich, uniform, and robust solid electrolyte interphase layer and fewer unfavorable decomposition products. As a result, this low‐concentration electrolyte significantly enhances electrochemical performances of Li||Li symmetric cells and high‐voltage LiCoO2||Li batteries. [ABSTRACT FROM AUTHOR]

Concentration of electrolyte has significant effects on performances of rechargeable batteries. Previous studies mainly focused on concentrated electrolytes. So far, only several recipes on low‐concentration electrolytes were studied, performing enhanced performance in advanced rechargeable batteries. Here, based on common electrolyte components, a low‐concentration electrolyte composed of 0.2 M lithium hexafluorophosphate (LiPF6) solvated in fluoroethylene carbonate (FEC) and ethyl methyl carbonate (EMC) is employed for high‐voltage Li metal battery. The synergistic working mechanisms of introducing fluorine‐containing solvent in the solvated structure and low salt concentration effect are revealed, resulting in LiF‐rich, uniform, and robust solid electrolyte interphase layer and fewer unfavorable decomposition products. As a result, this low‐concentration electrolyte significantly enhances electrochemical performances of Li||Li symmetric cells and high‐voltage LiCoO2||Li batteries. [ABSTRACT FROM AUTHOR]

[Display omitted] As alloying-type anode materials, metallic aluminum owns an ultra-high specific capacity (993 mAh g A l - 1 to LiAl) for Li storage, which is low-cost and a promising candidate for next-generation rechargeable batteries with high energy densities. However, metallic Al anodes suffer from irreversible lithiation of naturally occurring alumina layer during cycles, resulting in rapid capacity decay of Al anode-based batteries. Herein, Li supplement nucleated on Al foil via a controllably electrochemical pre-lithiation technology is employed for achieving high-performance elemental foil anodes. In full batteries, the pre-lithiated areas continuously supply Li outward during dealloying process to compensate for irreversible lithium loss during alloying process that preferentially alloys the unreacted Al 2 O 3 surface layer along the rolling direction of Al foil until the entire surface is covered by Li x AlO y. This lithiation behavior can avoid the severe stress concentration during alloying to prevent the perforation and pulverization of foil, making commercial Al foil succeed as single-material anodes. The produced commercial Al foil anode-based Li-ion batteries employing various commercial cathodes demonstrate promising electrochemical performances. For example, the Al||LiNi 0.8 Co 0.1 Mn 0.1 O 2 battery offers a high specific capacity of 180 mAh g−1, an excellent capacity retention of ∼90% after 400 cycles, and relatively stable solid electrolyte interface without any dendrite. [ABSTRACT FROM AUTHOR]