Wang Zhongming, He Zhiyuan, Wang Zhongsheng, Yang Jixu, Long Kecheng, Wu Zhibin, Zhou Gang, Mei Lin, Chen Libao
State Key Laboratory of Powder Metallurgy, Central South University Changsha 410083 P. R. China
School of Materials Science and Engineering, Dongguan University of Technology Dongguan 523000 P. R. China.
Chem Sci. 2024 Jul 29;15(34):13768-13778. doi: 10.1039/d4sc03890h. eCollection 2024 Aug 28.
Lithium-ion batteries (LIBs) are extensively employed in various fields. Nonetheless, LIBs utilizing ethylene carbonate (EC)-based electrolytes incur capacity degradation in a wide-temperature range, which is attributable to the slow Li transfer kinetics at low temperatures and solvent decomposition during high-rate cycling at high temperatures. Here, we designed a novel electrolyte by substituting nitrile solvents for EC, characterized by low de-solvation energy and high ionic conductivity. The correlation between the carbon chain length of nitrile solvents with reduction stability and the Li-solvated coordination was investigated. The results revealed that the valeronitrile (VN) solvent displayed an enhanced lowest unoccupied molecular orbital energy level and low de-solvation energy, which helped construct robust SEI interfacial layers and improved kinetics of interfacial ion transfer in wide-temperature LIBs. The VN-based electrolyte employed in graphite‖NCM523 pouch cells achieved a discharge capacity of 89.84% at a 20C rate at room temperature. Meanwhile, the cell exhibited 3C rate cycling stability even at a high temperature of 55 °C. Notably, the VN-based electrolyte exhibited a high ionic conductivity of 1.585 mS cm at -50 °C. The discharge capacity of pouch cells retained 75.52% and 65.12% of their room temperature capacity at -40 °C and -50 °C, respectively. Wide-temperature-range batteries with VN-based electrolytes have the potential to be applied in various extreme environments.
锂离子电池（LIBs）被广泛应用于各个领域。然而，使用碳酸乙烯酯（EC）基电解质的锂离子电池在很宽的温度范围内会出现容量衰减，这是由于低温下锂传输动力学缓慢以及高温下高速循环过程中溶剂分解所致。在此，我们通过用腈类溶剂替代EC设计了一种新型电解质，其特点是去溶剂化能低且离子电导率高。研究了腈类溶剂的碳链长度与还原稳定性以及锂溶剂化配位之间的关系。结果表明，戊腈（VN）溶剂显示出增强的最低未占据分子轨道能级和低去溶剂化能，这有助于构建坚固的固体电解质界面（SEI）界面层，并改善宽温锂离子电池中界面离子转移的动力学。用于石墨‖NCM523软包电池的VN基电解质在室温下以20C倍率实现了89.84%的放电容量。同时，该电池即使在55℃的高温下也表现出3C倍率的循环稳定性。值得注意的是，VN基电解质在-50℃时表现出1.585 mS cm的高离子电导率。软包电池在-40℃和-50℃时的放电容量分别保留了其室温容量的75.52%和65.12%。具有VN基电解质的宽温范围电池有潜力应用于各种极端环境。
