3 research outputs found
High-Performance Cells Containing Lithium Metal Anodes, LiNi<sub>0.6</sub>Co<sub>0.2</sub>Mn<sub>0.2</sub>O<sub>2</sub> (NCM 622) Cathodes, and Fluoroethylene Carbonate-Based Electrolyte Solution with Practical Loading
We
report on the highly stable lithium metal|LiNi<sub>0.6</sub>Co<sub>0.2</sub>Mn<sub>0.2</sub>O<sub>2</sub> (NCM 622) cells with practical
electrodes’ loading of 3.3 mA h g<sup>–1</sup>, which
can undergo many hundreds of stable cycles, demonstrating high rate
capability. A key issue was the use of fluoroethylene carbonate (FEC)-based
electrolyte solutions (1 M LiPF<sub>6</sub> in FEC/dimethyl carbonate).
Li|NCM 622 cells can be cycled at 1.5 mA cm<sup>–2</sup> for
more than 600 cycles, whereas symmetric Li|Li cells demonstrate stable
performance for more than 1000 cycles even at higher areal capacity
and current density. We attribute the excellent performance of both
Li|NCM and Li|Li cells to the formation of a stable and efficient
solid electrolyte interphase (SEI) on the surface of the Li metal
electrodes cycled in FEC-based electrolyte solutions. The composition
of the SEI on the Li and the NCM electrodes is analyzed by X-ray photoelectron
spectroscopy and Fourier transform infrared spectroscopy. A drastic
capacity fading of Li|NCM cells is observed, followed by spontaneous
capacity recovery during prolonged cycling. This phenomenon depends
on the current density and the amount of the electrolyte solution
and relates to kinetic limitations because of SEI formation on the
Li anodes in the FEC-based electrolyte solution