Design and Reaction Mechanism of Rechargeable Lithium-Carbon Fluoride Battery.

Su, Wei; Wang, Dongxiao; Li, Yuanhang; Mao, Huican; Wei, Bingxin; Xu, Shuyin; Lu, Shigang; Guo, Bingkun et al. · ACS Nano · 2024

basic_science · Level V

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Abstract

Recharging primary batteries is of great importance for increasing the energy density of energy storage systems to power electric aircraft and beyond. Carbon fluoride (CF<i><sub>x</sub></i>) cathodes are characterized by high specific capacity and energy density (865 mAh g<sup>-1</sup> and 2180 Wh kg<sup>-1</sup>, respectively). Preventing the crystallization of LiF with an intermediate and lowering the energy barrier from LiF to CF<i><sub>x</sub></i> is expected to render the Li/CF<i><sub>x</sub></i> battery reversible. In this study, taking the advantage of a high-voltage-stable all-fluorinated electrolyte containing the boron-based anion receptor tris(trimethylsilyl)borate (TMSB), a rechargeable Li/CF<i><sub>x</sub></i> battery was realized with a reversible capacity of 465.9 mAh g<sup>-1</sup> and an energy density of 1183.9 Wh kg<sup>-1</sup>, approximately 53% of that in the first discharge. After the first discharge, the charge-discharge profile featured rechargeable characteristics. <i>In situ</i> X-ray diffraction, <i>ex situ</i> soft X-ray absorption spectroscopy, pair distribution function analysis, and other measurements confirmed the generation and decomposition of Li-F and C-F bonds during cycling. Density functional theory calculations and nuclear magnetic resonance spectroscopy confirmed that TMSB serves as an anion carrier through the generation of a [TMSB-F]<sup>-</sup> complex, facilitating the conversion reactions during cycling. This study demonstrated a facile and low-cost approach for realizing high-energy-density, reversible Li/CF<i><sub>x</sub></i> batteries.