Transport and interface characteristics of Te-doped NASICON solid electrolyte Li1.3Al0.3Ti1.7(PO4)3

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.

Facile Route to Synthesize a Highly Sinterable Li1.3Al0.3Ti1.7(PO4)3 Solid Electrolyte

NASICON-type Li1.3Al0.3Ti1.7(PO4)3 (LATP) is a widely used solid electrolyte in solid-state lithium batteries, owing to its excellent chemical stability against moisture and high total ionic conductivity. However, traditionally, densification of LATP has been achieved through a high-temperature sintering process (approximately 1000 °C) owing to its poor sinterability. Herein, we report a facile synthesis route to obtain highly sinterable LATP solid electrolyte using tetrabutyl titanate (C16H36O4Ti) as the titanium source and incorporating the traditional solid-state reaction method. The synthetic LATP powder mixed with a low ratio of LiTiPO5 exhibited a hybrid crystalline-amorphous phase structure, which facilitated grain fusion, promoted structural homogeneity, and facilitated structural densification under low-temperature sintering. The sintered LATP pellet, which exhibited an interconnected structure and indistinct grain boundaries, achieved a relative density of >90% and an ionic conductivity of 0.667 mS/cm at a sintering temperature of only 750 °C. Additionally, we systematically studied and demonstrated the synthesis reaction mechanism, sintering behavior, and ionic diffusion kinetics of LATP electrolytes. Our study paves the way for synthesizing highly sinterable LATP solid electrolytes using a simple, additive-free, and cost-effective method.

Insight into Dendrites Issue in All Solid-State Batteries with Inorganic Electrolyte: Mechanism, Detection and Suppression Strategies

All solid-state batteries (ASSBs) are regarded as one of the promising next-generation energy storage devices due to their expected high energy density and capacity. However, failures due to unrestricted growth of lithium dendrites (LDs) have been a critical problem. Moreover, the understanding of dendrite growth inside solid-state electrolytes is limited. Since the dendrite process is a multi-physical field coupled process, including electrical, chemical, and mechanical factors, no definitive conclusion can summarize the root cause of LDs growth in ASSBs till now. Herein, the existing works on mechanism, identification, and solution strategies of LD in ASSBs with inorganic electrolyte are reviewed in detail. The primary triggers are thought to originate mainly at the interface and within the electrolyte, involving mechanical imperfections, inhomogeneous ion transport, inhomogeneous electronic structure, and poor interfacial contact. Finally, some of the representative works and present an outlook are comprehensively summarized, providing a basis and guidance for further research to realize efficient ASSBs for practical applications.

Electrochemical Properties of an Sn-Doped LATP Ceramic Electrolyte and Its Derived Sandwich-Structured Composite Solid Electrolyte

An Li_1.3Al_0.3Sn_xTi_1.7−x(PO₄)₃ (LATP-xSn) ceramic solid electrolyte was prepared by Sn doping via a solid phase method. The results showed that adding an Sn dopant with a larger ionic radius in a concentration of x = 0.35 enabled one to equivalently substitute Ti sites in the LATP crystal structure to the maximum extent. The uniform Sn doping could produce a stable LATP structure with small grain size and improved relative density. The lattice distortion induced by Sn doping also modified the transport channels of Li ions, which promoted the increase of ionic conductivity from 5.05 × 10⁻⁵ to 4.71 × 10⁻⁴ S/cm at room temperature. The SPE/LATP-0.35Sn/SPE composite solid electrolyte with a sandwich structure was prepared by coating, which had a high ionic conductivity of 5.9 × 10⁻⁵ S/cm at room temperature, a wide electrochemical window of 4.66 V vs. Li/Li⁺, and a good lithium-ion migration number of 0.38. The Li||Li symmetric battery test results revealed that the composite solid electrolyte could stably perform for 500 h at 60 °C under the current density of 0.2 mA/cm², indicating its good interface stability with metallic lithium. Moreover, the analysis of the all-solid-state LiFePO₄||SPE/LATP-0.35Sn/SPE||Li battery showed that the composite solid electrolyte had good cycling stability and rate performance. Under the conditions of 60 °C and 0.2 C, stable accumulation up to 200 cycles was achieved at a capacity retention ratio of 90.5% and a coulombic efficiency of about 100% after cycling test.