High Voltage Electrolytes Development for High-Ni Cathodes

Electrolytes connect the two electrodes in a lithium battery by providing Li⁺ transport channels between them. Recently, ether-based localized high-concentration electrolytes have been developed for lithium-metal batteries and show a great success. Despite their high Coulombic efficiency (~ 99.5%) with lithium metal, the relatively high highest occupied molecular orbital (HOMO) of ethers limits their application at high voltages (> 4.4 V). To tackle this issue, we proposed a new concept of electrolyte, namely localized saturated electrolyte (LSE), based on carbonate solvents that have lower HOMO levels than ether solvents. The formation of a special Li⁺solvation structure can further reduce the HOMO level of the electrolyte, increasing its oxidative stability. We demonstrate that the developed LSE can stabilize various types of cathodes at high voltages up to 4.85 V. Materials characterizations were further conducted to uncover the mechanisms. And 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. Our work highlights the importance of developing advanced electrolytes for stabilizing cathodes at high voltages in next-generation batteries.