In-Situ Electrochemical Customization of Solid Electrolyte Interphase for Fast-Charging and Long-Cycle-Life Graphite Anodes

Abstract

The burgeoning demand for electric vehicles and electronics underscores the imperative for fast-charging graphite (Gr)-based lithium-ion batteries (LIBs) to alleviate “range anxiety”. Overcoming the fast-charging challenge necessitates tackling diffusion issues, notably the sluggish lithium-ion (Li⁺) transport through solid electrolyte interphase (SEI). In response, our work proposes a charge/discharge protocol that in-situ accurately customizes an inner-LiF-rich bilayer SEI in a commercial carbonate electrolyte without introducing additional functional additives to reduce the energy barrier for Li⁺ migration and thus enable fast-charging capabilities for Gr anode. Moreover, our study reveals strong structure-dependent properties of the SEI on the Gr, including interface affinity, Li⁺ transport, and electrical insulation, which helps to design high-ion-conductivity and stable SEI. As a result, the in-situ electrochemical customization of the inner-LiF-rich bilayer SEI significantly increases the cycling stability and rate performance of Gr anode, maintaining a high capacity retention of 70.6% after 1000 cycles at a high rate of 5 C. Moreover, the LiNi_0.6Co_0.2Mn_0.2O₂ (NCM622)||Gr pouch cell utilizing the new formation protocol demonstrates a 9.5% increase in capacity retention compared to the traditional charge/discharge formation protocol. Our work provides an effective and scalable strategy for advancing fast-charging capabilities and extending the longevity of Gr-based LIBs.