Changfei Zou,Zihao Zang,Xiyuan Tao,Lingguang Yi,Xiaoyi Chen,Xiaoyan Zhang,Li Yang,Xianhu Liu,Xianyou Wang
All-solid-state lithium batteries (ASSLBs) composed of sulfide-based solid-state electrolyte and LiNixMnyCo1–x–yO2 (NMC) cathode are expected to become the promising next generation of energy storage systems due to their great potential in highly improved safety and energy density. However, the poor interfacial stability between the NMC cathode and sulfide-based electrolyte remains an important challenge for the commercialization of ASSLBs. In this study, a thin layer of fast lithium-ion conductor Li1.3Al0.3Ti1.7(PO4)3 (LATP) with a thickness of 8 nm was coated at the interface between LiNi0.8Co0.1Mn0.1O2 (NCM811) and Li5.5PS4.5Cl1.5 via a facile wet chemical method to improve interfacial stability. It has been found that the nanoscale LATP coating layer can not only accelerate lithium ions across the NCM811/Li5.5PS4.5Cl1.5 interface but also effectively alleviate the interfacial problems. The initial discharge capacity of the as-prepared LATP@NCM811/Li5.5PS4.5Cl1.5/Li batteries at 0.1 C is 151.5 mAh/g, and the capacity retention rate is 81.6% after 100 cycles at room temperature. The results indicate that interfacial modification with the nanosized LATP coating is an effective strategy for providing more possibilities for commercial application of ASSLBs.
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.
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