Synergistic Dual Electrolyte System of LATP and In- Situ Solod-State PDOL System and its Improvement on the Performance of NCM811 Batteries

Graphical 2,2,2-trifluoroethyl phosphite (DETFPi), 1,3-Dioxolane (DOL) and trimethylolpropane tri(methacrylate) (TTE) were polymerized under LiBF 4 initiator on the LATP/PE/LATP separator and thereby obtained DETFPi-PDOL/LATP composite electrolyte after 24 h at room temperature. LATP coating on the surface of the PE separator can improve the cycling stability, rate performance, and interface state of NCM811 batteries. 1,3-Dioxolane (DOL) can undergo in-situ polymerization in batteries to form solid-state organic electrolyte PDOL. When applied to NCM811||Li battery system, PDOL electrolyte helps optimize the contact and interface stability between electrolyte and electrodes. This study explores the effects of PDOL with PE separators coated with Li1 .3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) on the performance of NCM811||Li batteries. 2,2,2-trifluoroethyl phosphite (DETFPi), was mixed with DOL at a 1 : 35 mass ratio. Then, LiBF 4 was used to initiate in-situ polymerization and thereby obtained DETFPi-PDOL electrolyte after 24 h at room temperature. The composite electrolyte exhibits enhanced ion conductivity (1.59×10 −4 S cm −1 ), high lithium ion transference number (0.78), wide electrochemical stability window (4.53 V), and high critical current density (2.2 mA cm −2 ). Li||PDOL@LATP||Li battery shows extremely low overpotential (35 mV) after a constant current stable cycle of 500 h at 1.0 mA cm −2 . After 500 cycles at 1 C, the remaining capacity is 153.9 mAh g −1 with a capacity retention of 82.1 % in NCM811||PDOL@LATP||Li batteries. This indicates that the LATP coating on the surface of the PE separator plays an important role in optimizing the performance of DETFPI-PDOL electrolyte batteries. LATP and DETFPI-PDOL are effective in improving the cycling stability, rate performance, and interface state of NCM811 batteries.