Enhanced ion-electron mixing interface for high energy solid-state lithium metal batteries

Construction of SnO2 buffer layer and analysis of its interface modification for Li and Li1.5Al0.5Ge1.5(PO4)3 in solid-state batteries

SnO2 layer between Li1.5Al0.5Ge1.5(PO4)3 (LAGP) and lithium anode was prepared through simple scratch-coating process to improve interface properties. The physical phase, morphology, and electrochemical properties of Li/SnO2/LAGP structure were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and electrochemical analytical methods. It was found that SnO2 layer effectively improved the interface stability of LAGP and lithium anode. The prepared Li/SnO2/LAGP/SnO2/Li symmetric cell exhibited a large critical current density of 1.8 mA cm-2 and demonstrated excellent cycling characteristics. The polarization voltages of symmetric cell were 0.1 V and 0.8 V after 1000 h of cycling at current densities of 0.04 mA cm-2 and 0.5 mA cm-2, respectively. Li/SnO2@LAGP/LiFePO4 solid-state full cells were also assembled, exhibiting a discharge specific capacity of 150 mAh g-1 after 200 cycles at 0.1C with capacity retention rate of 96 %. The good interface properties of Li/SnO2/LAGP structure are attributed to the transformation of SnO2 layer into a buffer layer containing Li2O, Sn0, and LixSny alloy during cycling process, which effectively inhibits the reduction reaction between LAGP and lithium anode.

Metal-Doped NASICON/Polymer Composite Solid Electrolyte for Lithium Titania Anode in Lithium-Ion Batteries

This study reports five types of metal-doped (Co, Cu, Sn, V, and Zr) NASICON-type Li1.3Al0.3Ti1.7(PO4)3 (LATP)/polymer composite solid electrolytes (CSEs) enabling Li4Ti5O12 (LTO) anodes to have high rate capability and excellent cycling performance. The high Li+-conductivity LATP samples are successfully synthesized through a modified sol-gel method followed by thermal calcination. We find that the cation dopants clearly influence the substitution of Al for Ti, with the type of dopant serving as a crucial factor in determining the ionic conductivity and interfacial resistance of the solid electrolyte. The CSE containing poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), and Sn-LATP shows an ionic conductivity of 1.88 × 10-4 S cm-1 at ambient temperature. The optimum conductivity can be attributed to alterations in the lattice parameters and Li+ transport pathways owing to Sn doping. The solid-state cell equipped with the LTO-supported CSE containing Sn-LATP fillers demonstrates both excellent high rate capability at 5 C (with a capacity retention of 86% compared to the value measured at 0.2 C) and superior cycling stability, maintaining high Coulombic efficiency (>99.0%) over 510 cycles. These findings indicate that the proposed CSE is highly promising for use in solid-state lithium batteries with desirable charge-discharge properties and high durability.

Preparation and Properties of Gel Polymer Electrolytes with Li1.5Al0.5Ge1.5(PO4)3 and Li6.46La3Zr1.46Ta0.54O12 by UV Curing Process

Poly (vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)-based gel polymer electrolytes (GPEs) are considered a promising electrolyte candidate for polymer lithium-ion batteries (LIBs) because of their free-standing shape, versatility, security, flexibility, lightweight, reliability, and so on. However, due to problems such as low ionic conductivity, PVDF-HFP can only be used on a small scale when used as a substrate alone. To overcome the above shortcomings, GPEs were designed and synthesized by a UV curing process by adding NASICON-type Li1.5Al0.5Ge1.5(PO4)3 (LAGP) and garnet-type Li6.46La3Zr1.46Ta0.54O12 (LLZTO) to PVDF-HFP. Experimentally, GPEs with 10% weight LLZTO in a PVDF-HFP matrix had an ionic conductivity of up to 3 × 10-4 S cm-1 at 25 °C. When assembled into LiFePO4/GPEs/Li batteries, a discharge-specific capacity of 81.5 mAh g-1 at a current density of 1 C and a capacity retention rate of 98.1% after 100 cycles at a current density of 0.2 C occurred. Therefore, GPEs added to LLZTO have a broad application prospect regarding rechargeable lithium-ion batteries.