Bonding Lithium Metal with Garnet Electrolyte by Interfacial Lithiophobicity/Lithiophilicity Transition Mechanism over 380 °C

In Situ Fabrication of High Ionic and Electronic Conductivity Interlayers Enabling Long-Life Garnet-Based Solid-State Lithium Batteries

Garnet-type Li6.75La3Zr1.75Ta0.25O12 (LLZTO) is a promising solid-state electrolyte (SSE) because of its fast ionic conduction and notable chemical/electrochemical stability toward the lithium (Li) metal. However, poor interface wettability and large interface resistance between LLZTO and Li anode greatly restrict its practical applications. In this work, we develop an in situ chemical conversion strategy to construct a highly conductive Li2S@C layer on the surface of LLZTO, enabling improved interfacial wettability between LLZTO and the Li anode. The Li/Li2S@C-LLZTO-Li2S@C/Li symmetric cell has a low interface impedance of 78.5 Ω cm2, much lower than the 970 Ω cm2 of a Li/LLZTO/Li cell. Moreover, the Li/Li2S@C-LLZTO-Li2S@C/Li cell exhibits a high critical current density of 1.4 mA cm-2 and an ultralong stability of 3000 h at 0.1 mA cm-2. When used in a LiFePO4 battery, the Li/Li2S@C-LLZTO/LiFePO4 battery exhibits a high initial discharge capacity of 150.8 mA h g-1 at 0.2 C without lithium storage capacity attenuation during 200 cycles. This work provides a novel and feasible strategy to address interface issues of SSEs and achieve lithium-dendrite-free solid-state batteries.

Dual Interface Compatibility Enabled via Composite Solid Electrolyte with High Transference Number for Long-Life All-Solid-State Lithium Metal Batteries

The development of solid-state electrolytes (SSEs) effectively solves the safety problem derived from dendrite growth and volume change of lithium during cycling. In the meantime, the SSEs possess non-flammability compared to conventional organic liquid electrolytes. Replacing liquid electrolytes with SSEs to assemble all-solid-state lithium metal batteries (ASSLMBs) has garnered significant attention as a promising energy storage/conversion technology for the future. Herein, a composite solid electrolyte containing two inorganic components (Li6.25Al0.25La3Zr2O12, Al2O3) and an organic polyvinylidene difluoride matrix is designed rationally. X-ray photoelectron spectroscopy and density functional theory calculation results demonstrate the synergistic effect among the components, which results in enhanced ionic conductivity, high lithium-ion transference number, extended electrochemical window, and outstanding dual interface compatibility. As a result, Li||Li symmetric battery maintains a stable cycle for over 2500 h. Moreover, all-solid-state lithium metal battery assembled with LiNi0.6Co0.2Mn0.2O2 cathode delivers a high discharge capacity of 168 mAh g-1 after 360 cycles at 0.1 C at 25 °C, and all-solid-state lithium-sulfur battery also exhibits a high initial discharge capacity of 912 mAh g-1 at 0.1 C. This work demonstrates a long-life flexible composite solid electrolyte with excellent interface compatibility, providing an innovative way for the rational construction of next-generation high-energy-density ASSLMBs.

Advances in Inorganic Solid-State Electrolyte/Li Interface

The increasing demand for high-energy-density and high-safety energy storage devices has sparked a growing interest in all-solid-state lithium metal batteries (ASSLMBs). A high-quality inorganic solid-state electrolyte (ISE) is a fundamental requirement for ASSLMBs, and an effective ISE/Li interface is a key factor in attaining high-performance ASSLMBs. In this Concept, we initially summarize the challenges encountered by ISE/Li interfaces and delineate four commonly employed strategies for modifying the ISE/Li interface. Then, we explore the merits and drawbacks of coatings utilized as ISE/Li interfacial phases. We also delve into the commonly employed thermal bonding and innovative cold bonding methods utilized for in situ interface preparation. Lastly, we spotlight future directions for enhancing the functionality of ISE/Li interfaces and achieving high-performance ASSLMBs.

1000 °C High-Temperature Wetting Behaviors of Molten Metals on Laser-Microstructured Metal Surfaces

The melting of metals at high temperatures is common and important in many fields, e.g., metallurgy, refining, casting, welding, brazing, even newly developed batteries, and nuclear fusion, which is thus of great value in modern industrialization. However, the knowledge of the wetting behaviors of molten metals on various substrate surfaces remains insufficient, especially when the temperature is over 1000 °C and with microstructured metal substrate surfaces. Herein, we selected molten cerium (Ce) on a tantalum (Ta) substrate as an example and investigated in detail its wetting at temperatures up to 1000 °C by modulating the microstructures of the substrate surfaces via laser processing. We discovered that the wetting states of molten Ce on Ta surfaces at temperatures over 900 °C could be completely altered by modifying the laser-induced surface microstructures and the surface compositions. The molten Ce turned superlyophilic with its contact angle (CA) below 10° on the only laser-microstructured surfaces, while it exhibited lyophobicity with a CA of about 135° on the laser-microstructured plus oxidized ones, which demonstrated remarkably enhanced resistance against the melt with only tiny adhesion in this circumstance. In contrast, the CA of molten Ce on Ta substrate surfaces only changed from ∼25 to ∼95° after oxidization without laser microstructuring. We proved that modulating the substrate surface microstructures via laser together with oxidization was capable of efficiently controlling various molten metals' wetting behaviors even at very high temperatures. These findings not only enrich the understanding of molten metal high-temperature wettability but also enable a novel practical approach to control the wetting states for relevant applications.