Enhancement of Cycling Performance by use of Li Anode with Additive Leaching-Type Polymer Layer for Lithium Metal Batteries

Rechargeable lithium batteries using lithium metal as an anode are attractive candidates for high energy density power sources in portable electronic devices and electric vehicles, because lithium metal offers a high specific capacity (~3,862 mAh g^-1) and possesses a low reduction potential. However, the development of rechargeable lithium metal batteries has been hindered by the high reactivity of lithium metal with liquid electrolytes and the occurrence of dendrite growth during charge and discharge cycles. Therefore, it is essential to form the stable solid electrolyte interphase (SEI) on lithium metal to prevent lithium dendrite growth and minimize side reactions of liquid electrolyte. Recently, various additives have been investigated to form a stable SEI layer on Li metal. However, during repetitive charge and discharge process, the additives in the electrolyte can be gradually depleted, resulting in capacity fading. In this work, we developed additive leaching-type polymer layer containing excessive amounts of additives that form the stable SEI layer. The additives can be stored in the polymeric layer, continuously released to the electrolyte during the repeated cycling. Electrochemical analyses such as linear sweep voltammetry and cyclic voltammetry were investigated, and the Li/Li symmetric cells showed the regulation of lithium deposition with small overpotential. The cycling performance of lithium metal batteries employing additive leaching-type polymer layer was evaluated with high nickel NCM cathode. Furthermore, characterization techniques such as cyclic voltammetry, X-ray photoelectron spectroscopy, ⁷Li nuclear magnetic resonance, and electrochemical impedance spectroscopy were employed to analyze the release behavior of additives and investigate the mechanisms associated with released additives for improvement of cycling performance.