Development of High-Capacity Rechargeable Battery with a Lithium Metal Anode

为了改善锂离子电池充放电性能的可逆性，通过物理或化学改性，对锂金属阳极/电解质界面进行了优化。研究结果如下：1. Li金属阳极/电解质界面物理化学结构的优化在PC-DMC体系中，用LiPF_6或Li（C_2F_5SO_2）_2N在-20℃下电沉积Li，然后对电沉积的Li进行低温循环，对Li金属阳极/电解质界面进行了改性。在-20℃下进行界面改性的锂金属阳极在25℃下循环后，LiPF_6/PC-DMC体系的循环寿命得到了提高。在有机电解质溶液中添加金属盐（MgI_2，AlI_3）可以提高锂沉积/溶解循环的库仑效率。在添加AlI_3的情况下，当AlI_3仅添加到第一次沉积的溶液中时，获得最高的循环寿命.锂金属阳极界面结构和电化学行为的电化学分析用CCD显微镜观察发现，低温电解液中的预循环提供了均匀的锂-金属界面，即使在25℃的温度下冲洗后，该界面仍保留在锂上。交流阻抗分析表明，AlI_3的加入有效地保持了重复循环后Li/电解质界面处的低电阻.有机电解液中集流体极化行为的影响研究了锂离子电池集流体铝在不同锂盐有机电解液中的阳极极化行为。在阳极极化条件下，Al集流体在Li（CF_3SO_2）_2N和Li（C_2F_5SO_2）_2N溶液中发生腐蚀，而在LiPF_6溶液中阳极稳定。

Improving the reversibility of charge-discharge properties, the optimization of a Li metal anode/electrolyte interface was investigated by modifying physically or chemically. The results are summarized as follows.1. Optimization for physical and chemical structure of Li metal anode/electrolyte interface A Li metal anode/electrolyte interface have been modified by electrodeposition of Li on a Ni substrate at a low temperature (-20℃) in PC-DMC with LiPF_6 or Li (C_2F_5SO_2)_2N and by the following Low-temperature cycling of electrodeposited Li. When a Li metal anode with the interface modified at -20℃ was cycle at 25℃, the cycle life of the anode in the LiPF_6/PC-DMC system was improved. Addition of metal salts (MgI_2, AlI_3) in organic electrolyte solutions has been examined to improve the coulombic efficiency for Li deposition/dissolution cycles. In the case of AlI_3 addition, the highest cycle life was obtained when AlI_3 was only added to the solution for the first deposition.2. Electrochemical analysis for interfacial structure and electrochemical behavior of Li metal anode Optical observation with a CCD microscope revealed that the precycling in the low-temperature electrolytes provided an uniform Li-interface which remained on Li even after a rinse in temperature to 25℃. The ac impedance analysis suggested that the addition of AlI_3 is effective to keep the resistance at the Li/electrolyte interface low after the repeated cycles.3. Effect of polarization behavior of current collector in organic electrolyte The anodic polarization behavior of Al as a current collector of Li ion battery has been investigated in organic electrolyte solutions containing different lithium salts. The AI current collector has suffered the corrosion in the solution containing Li (CF_3SO_2)_2N and Li (C_2F_5SO_2)_2N under an anodic polarization condition, whereas it was anodically stable in the LiPF_6 solution.