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

Abstract

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_.3Al_0.3Ti_1.7(PO₄)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, LiBF₄ 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.