Electrochemical Conversion of Nitrogen Trifluoride as a Gas-to-Solid Cathode in Li Batteries

Abstract

Nonaqueous metal-gas batteries have emerged as a growing family of primary and rechargeable batteries with high capacities and energy densities. We herein report a high-capacity primary Li-gas battery that uses a perfluorinated gas, nitrogen trifluoride (NF), as the cathode reactant. Gravimetric capacities of ∼1100 and 4000 mAh/g are achieved at 25 and 55 °C, respectively (at 20 mA/g), with discharge voltages up to 2.6 V vs Li/Li. NF reduction occurs by a 3e/NF process, yielding polycrystalline lithium fluoride (LiF) on a carbon cathode. The detailed electrochemical NF conversion mechanism is proposed and supported by solid- and liquid-phase characterization and theoretical computation, revealing the origin of observed discharge overpotentials and elucidating the significant contribution of N-F bond cleavage. These findings indicate the value of exploring fluorinated gas cathodes for primary batteries; moreover, they open new avenues for future targeted electrocatalyst design and cathode materials synthesis applications benefiting from conformal coatings of LiF.

Fluorinated graphene nanoribbons from unzipped single-walled carbon nanotubes for ultrahigh energy density lithium-fluorinated carbon batteries

“…Among various solid cathode materials, fluorinated carbon (CF x ) has attracted unprecedent attention due to their high theoretical energy density, which is much higher than that of lithium ion batteries (~500 W h kg −1 ) [3]. To fill this short-term technology gap for producing batteries with higher energy densities, several types of nonaqueous metal-gas batteries have been explored to meet growing demands, such as Li-O 2 [4], Na-O 2 [5], K-O 2 [6], Li-CO 2 [7,8], Li-NF 3 [9], and Li-SF 6 [10][11][12]. However, the gas-to-solid conversion reaction involves a solution-mediated electrochemical process that induces complex thermodynamics, kinetics, and transport considerations, and it remains a challenge to achieve the potential energy densities and realize practical applications for these systems.…”

Nitrogen Triflorida (NF3) : Termodinamika dan Transpor Elektron NF3

“…Nitrogen trifluorida (5)(6)(7)(8)(9) adalah suatu senyawa anorganik dengan rumus NF 3 . Senyawa nitrogen (13)(14)(15) fluor (16)(17)(18) ini adalah gas tak berwarna, tak berbau dan tidak mudah terbakar.…”

“…Nitrogen trifluorida (5)(6)(7)(8)(9) adalah senyawa anorganik (11; 12) dengan rumus molekul NF 3 . NF 3 merupakan senyawa yang tidak berwarna, tidak berbau, gas mudah terbakar.…”

Electrochemical Fluoridation of Manganese Oxide by Perfluorinated‐Gas Conversion for Lithium‐Ion Cathodes

“…To test this hypothesis, and to examine another possible fluoridation methodology with potential to help elucidate the limitations of those used so far, this study investigated whether higher degrees of fluoridation, as evidenced by higher discharge capacities, are achievable using an electrochemically sourced LiF formed by reduction of perfluorinated gases. Recently, we have found that the full reduction of SF 6 (SF 6 + 8e À + 8Li + !Li 2 S + 6LiF) [13] and NF 3 (NF 3 + 3e À + 3Li + !3LiF + 1 = 2 N 2 ) [14] occurs on carbon cathodes at potentials of 2-3 V vs. Li/Li + , thus the gases act as a highly-F-dense and electroactive molecular LiF source. Moreover, the morphology of the electrochemically formed LiF, which nucleates and grows as nanoscale particles (with diameters ranging from 20 nm to > 400 nm) on the cathode substrate, was found to be highly versatile and could be tailored by modulating conditions such as electrolyte, discharge rate, and capacity.…”