Highly conductive thin composite solid electrolyte with vertical Li7La3Zr2O12 sheet arrays for high-energy-density all-solid-state lithium battery

To achieve high energy density of all-solid-state lithium batteries, solid-state electrolytes (SSEs) are required to be thin and highly conductive. Although constructing efficient inorganic Li-ion transfer network can provide excellent conductivity for SSEs, it is still challenging for these SSEs to simultaneously realize thin thickness and mechanical stability. Herein, well-ordered vertical Li7La3Zr2O12 sheet arrays (VLSA) were prepared, followed by introducing triple-layer ion-conducting polymers to fabricate 8 μm-thick VLSA composite solid electrolyte (CSE). We demonstrate that vertical and short VLSA (major path, accounting for 71.4% of Li-ion transfer) and VLSA/polymer interface (minor path, 27.8%) contribute to the high ionic conductivity of 2.60 × 10−4 S cm−1 and ionic conductance of 0.5 S at 30 °C, ranking one of the highest values among reported SSEs. The stiff VLSA enhances the mechanical strength of CSE, while the polymer existing in VLSA channels serves as a deformable buffer, endowing CSE with bendable property. Besides, the trilayer polymer structure permits this electrolyte to be compatible with lithium anode and high-voltage cathode. Therefore, the high-loading LiNi0.5Co0.2Mn0.3O2 (NCM523) cell can be cycled with limited lithium anode (N/P ratio = 1.18) over 158 cycles with capacity retention upon 80%, realizing a high energy density of 458.4 Wh kg−1.