He Mingfu, Li Yuanda, Guo Rui, Gallant Betar M
Department of Mechanical Engineering , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States.
J Phys Chem Lett. 2018 Aug 16;9(16):4700-4706. doi: 10.1021/acs.jpclett.8b01897. Epub 2018 Aug 3.
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.
非水金属-气体电池已成为一类不断发展的一次电池和可充电电池，具有高容量和能量密度。我们在此报告一种高容量一次锂-气体电池，它使用全氟化气体三氟化氮（NF₃）作为阴极反应物。在25和55°C下（电流密度为20 mA/g），分别实现了约1100和4000 mAh/g的重量容量，相对于Li/Li⁺的放电电压高达2.6 V。NF₃通过3e⁻/NF₃过程还原，在碳阴极上生成多晶氟化锂（LiF）。通过固相和液相表征以及理论计算提出并支持了详细的电化学NF₃转化机制，揭示了观察到的放电过电位的来源，并阐明了N - F键断裂的重要贡献。这些发现表明了探索用于一次电池的氟化气体阴极的价值；此外，它们为未来有针对性的电催化剂设计和阴极材料合成应用开辟了新途径，这些应用受益于LiF的保形涂层。
