Advanced Electrolyte Development for Next-generation Lithium Batteries

Electrolytes connect the two electrodes in a lithium battery by providing Li⁺ transport channels between them. Advanced electrolytes are being explored with high-Ni cathodes and lithium-metal anodes to meet the high energy density and cycle life goals, but the origin of the performance differences with different electrolytes is not fully understood. In this study, we explored the effect of electrolyte on Li plating morphology and its crystallinity, interphase chemistry on both electrodes, and surface degradation of high-Ni cathodes. We found that advanced electrolytes help form close-packed homogeneous Li morphology on the anode, generate thin and inorganic-rich interphase layers on both electrodes, and reduce surface degradation into spinel and rock-salt phases of high-Ni cathodes, leading to superior cycling performance of lithium batteries. Based on these understandings, we proposed a new concept of electrolyte, namely localized saturated electrolyte (LSE), which can increase the cycle life of lithium batteries based on the Co-free LiNiO₂ cathode by almost an order of magnitude. For example, compared to the conventional electrolyte that retains only 55% of the initial capacity after 200 cycles, the LSE retains a record 81% of the initial capacity after 600 deep cycles at 4.4 V (versus Li/Li⁺). Our work highlights the importance of developing advanced electrolytes for next-generation batteries.