Solid (cyanomethyl)trimethylammonium salts for electrochemically stable electrolytes for lithium metal batteries
Solid (cyanomethyl)trimethylammonium salts for electrochemically stable electrolytes for lithium metal batteries
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用于锂金属电池电化学稳定电解质的固体（氰甲基）三甲基铵盐
DOI：
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
M. Forsyth
中科院分区：
文献类型：
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作者：
Ruhamah Yunis;J. Pringle;Xiaoen Wang;Gaetan M. A. Girard;R. Kerr;Haijin Zhu;P. Howlett;D. Macfarlane;M. Forsyth
有机盐被认为是可充电锂金属电池（LMB）中的电解质溶剂。这是由于它们的不可燃性、不挥发性、宽的电化学窗口、良好的离子电导率和在固体（或准固体）状态下操作的可能性，使它们成为替代常规电解质中存在的当前易燃和有毒溶剂的有希望的候选物。采用一步阴离子复分解法合成了一系列新型的五种不同阴离子的固体氰铵盐。通过热重分析（TGA）、差示扫描量热法（DSC）、电化学阻抗谱（EIS）和拉曼光谱对所有盐进行了研究。用[FSI]-、[BF 4]-、[PF 6]-和[OTf]-阴离子获得固体盐，而含[DCA]-的盐作为低熔点固体获得。与类似铵盐的热和物理性质进行了比较。用固态核磁共振谱（NMR）研究了[DCA]-、[FSI]-、[BF 4]-和[PF 6]-阴离子的氰基铵盐。选择[N111 CN][BF 4]和[N111 CN][FSI]与相同阴离子的锂盐（10和50摩尔% Li+）混合。用DSC和EIS对四种电解质进行了研究。获得在[N111 CN][FSI]中的50摩尔% LiFSI作为液体电解质，并且在50 ° C下显示3 × 10 - 3S cm-1的离子电导率，在50 ° C下锂迁移数为0.37 ± 0.02。在[N111 CN][BF 4]中的准固体电解质50摩尔% LiBF 4在90 ° C下显示出0.78 × 10−3 S cm−1的离子电导率，在90 ° C下的迁移数为0.27 ± 0.02。除了使用各种电池配置的纽扣电池测试之外，还使用线性扫描伏安法（LSV）研究了这些材料的电化学性质。LSV测量显示高达5.6V（相对于Li+/Li）的高氧化稳定性，而Li金属对称电池循环和Li| Cu库仑效率（CE）测量证明了锂金属的稳定循环，在50 °C下CE为91 ± 1%。最后，初步结果表明，这些电解质的适用性，以全电池设备得到使用锂|具有1.0 mA h cm-2的中等面积容量的NMC 622电池，由此实现了在50 °C下以C/2的速率进行15次循环的全容量循环。
Organic salts are being considered for the electrolyte solvent in rechargeable lithium-metal batteries (LMBs). This is due to their non-flammability, non-volatility, wide electrochemical window, good ionic conductivity and the possibility of operating while in a solid (or quasi-solid) state making them promising candidates to replace current flammable and toxic solvents present in conventional electrolytes. A series of novel solid cyano-ammonium salts with five different anions were synthesized by one-step anion metathesis. All salts were studied by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), electrochemical impedance spectroscopy (EIS) and Raman spectroscopy. Solid salts were obtained with [FSI]−, [BF4]−, [PF6]− and [OTf]− anions, while the [DCA]− containing salt was obtained as a low melting point solid. Comparison of the thermal and physical properties with analogous ammonium salts was made. The cyano-ammonium salts with [DCA]−, [FSI]−, [BF4]− and [PF6]− anions were studied by solid-state nuclear magnetic resonance spectroscopy (NMR). [N111CN][BF4] and [N111CN][FSI] were selected for mixing with lithium salts (10 and 50 mol% Li+) of the same anion. The four resultant electrolytes were studied by DSC and EIS. The 50 mol% LiFSI in [N111CN][FSI] was obtained as a liquid electrolyte and displayed an ionic conductivity of 3 × 10−3 S cm−1 at 50 °C with a lithium transference number of 0.37 ± 0.02 at 50 °C. The quasi-solid electrolyte 50 mol% LiBF4 in [N111CN][BF4] displayed an ionic conductivity of 0.78 × 10−3 S cm−1 at 90 °C with a transference number of 0.27 ± 0.02 at 90 °C. The electrochemical properties of these materials were investigated using linear sweep voltammetry (LSV) in addition to coin cell testing using various cell configurations. LSV measurements showed high oxidative stability up to 5.6 V (vs. Li+/Li), while Li metal symmetric cell cycling and Li|Cu coulombic efficiency (CE) measurements demonstrated the stable cycling of lithium metal with a CE of 91 ± 1% at 50 °C. Finally, preliminary results showing the applicability of these electrolytes to full cell devices were obtained using Li|NMC622 cells with a moderate areal capacity of 1.0 mA h cm−2, whereby full capacity cycling for 15 cycles at a rate of C/2 at 50 °C was achieved.