Electrochemical Characteristics of Composite Solid Polymer Electrolytes Containing 1-Dimensional Active Ceramic Filler for All-Solid-State Lithium-Ion Batteries

Abstract

Recently, the battery market for electric vehicle (EV) and energy storage system (ESS) is expanding. In addition, attempts and studies to implement a high energy density by applying a lithium metal anode to a Li-ion battery (LIB) system are in progress. However, the conventional organic liquid electrolytes have safety problems, such as a short circuit due to lithium dendrite growth, and a risk of ignition and explosion due to electrolyte leakage. To address the issues, all-solid-state batteries (ASSBs) using stable solid electrolytes have attracted much attention as new-generation batteries. Among solid electrolytes, composite solid polymer electrolyte (CSPE) has excellent merits over existing liquid electrolytes such as no electrolyte leakage, non-flammability, and a wide electrochemical potential window. In addition, various types of inorganic fillers may be introduced to improve electrochemical properties of CSPEs. In this study, the CSPEs were fabricated by incorporating 1D or OD Li0.33La0.557Ti0.99Al0.01O3 (A-LLTO) perovskite solid electrolyte fillers in a PVDF-HFP polymer matrix and their electrochemical properties were investigated. The optimized 1D A-LLTO containing CSPE (1D A-LLTO CSPE) exhibited a high ionic conductivity of 0.21 mS cm-1, a good potential stability of up to 4.87 V for Li/Li+, and a lithium ion transport number of 0.499 at 50 °C. In addition, 1D A-LLTO CSPE showed better thermal stability and electrochemical properties compared with 0D A-LLTO CSPE. The 1D A-LLTO CSPE exhibited a reduced overpotential of about 45 mV for 1000 h in contact with lithium metal at 50 °C. Furthermore, the Li/1D A-LLTO CSPE/NCM622 full cell exhibited satisfactory rate capability, cycling stability with a discharge capacity of 159.95 mAh g-1 and a coulombic efficiency of 97.6% over 100 cycles at a rate of 0.2 C, and performed stable long-term cycling performance at the rate of 0.5 C over 400 cycles at 50 ℃. These results demonstrate that the 1D A-LLTO CSPE is expected to become one of the hopeful candidates for ASSBs.