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

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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.