Boosting practical high voltage lithium metal batteries by butyronitrile in ether electrolytes via coordination, hydrolysis of C≡N and relatively mild concentration strategy

Abstract Currently ether solvents have been regarded as the most compatible organic solvents with lithium metal in electrolytes of lithium batteries. However, ether solvents are unstable under high voltage (> 4.0 V), and prone to side reactions with nickel-rich high-voltage cathode materials. In this work, a novel dual-solvent electrolyte in ethylene glycol dimethyl ether (DME) and butyronitrile (BN) mixed solvent was designed and fabricated for Li/LiNi0.5Mn0.3Co0.2O2-based lithium metal batteries. When charged to high voltage 4.3 V, the battery cycled in this optimal electrolyte can maintain the capacity at 133.7 mAh g−1 with a retention of 88.84% after 150 cycles at 0.2 C and −10 °C. During long-term cycling, the battery also exhibits excellent cycling performance with capacity maintained at about 112.0 mAh g−1 after 500 cycles at 1 C and −10 °C. BN has strong oxidation resistance and high conductivity, which can inhibit the decomposition of ether solvents under high voltage and improve the low temperature performance of battery effectively. Additionally, the cyano (–C≡N) group in BN molecular has a strong coordination ability with the high-valent metal ions and can mask the active ions on the cathode, correspondingly reducing the corrosion of cathode material by the electrolyte. Moreover, cyano group can participate in the hydrolysis to remove trace amounts of water and acidic by-products such as HF in the electrolyte. Therefore, the boosting effect of butyronitrile for ether solvents can provide a promising strategy for enhancing the performance of high voltage lithium metal batteries for practical industrialization.