Garnet-Based Solid-State Li Batteries with High-Surface-Area Porous LLZO Membranes

Rechargeable garnet-based solid-state Li batteries hold immense promise as nonflammable, nontoxic, and high energy density energy storage systems, employing Li7La3Zr2O12 (LLZO) with a garnet-type structure as the solid-state electrolyte. Despite substantial progress in this field, the advancement and eventual commercialization of garnet-based solid-state Li batteries are impeded by void formation at the LLZO/Li interface at practical current densities and areal capacities beyond 1 mA cm-2 and 1 mAh cm-2, respectively, resulting in limited cycling stability and the emergence of Li dendrites. Additionally, developing a fabrication approach for thin LLZO electrolytes to achieve high energy density remains paramount. To address these critical challenges, herein, we present a facile methodology for fabricating self-standing, 50 μm thick, porous LLZO membranes with a small pore size of ca. 2.3 μm and an average porosity of 51%, resulting in a specific surface area of 1.3 μm-1, the highest reported to date. The use of such LLZO membranes significantly increases the Li/LLZO contact area, effectively mitigating void formation. This methodology combines two key elements: (i) the use of small pore formers of ca. 1.5 μm and (ii) the use of ultrafast sintering, which circumvents ceramics overdensification using rapid heating/cooling rates of ca. 50 °C per second. The fabricated porous LLZO membranes demonstrate exceptional cycling stability in a symmetrical Li/LLZO/Li cell configuration, exceeding 600 h of continuous operation at a current density of 0.1 mA cm-2.

Ultrafast Sintering for Ceramic-Based All-Solid-State Lithium-Metal Batteries

Long processing time and high temperatures are often required in sintering ceramic electrolytes, which lead to volatile element loss and high cost. Here, an ultrafast sintering method of microwave-induced carbothermal shock to fabricate various ceramic electrolytes in seconds is reported. Furthermore, it is also possible to integrate the electrode and electrolyte in one step by simultaneous co-sintering. Based on this ultrafast co-sintering technique, an all-solid-state lithium-metal battery with a high areal capacity is successfully achieved, realizing a promising electrochemical performance at room temperature. This method can extend to other various ceramic multilayer-based solid devices.

High-Temperature Ultrafast Sintering: Exploiting a New Kinetic Region to Fabricate Porous Solid-State Electrolyte Scaffolds

Solid-state batteries (SSBs) promise better safety and potentially higher energy density than the conventional liquid- or gel-based ones. In practice, the implementation of SSBs often necessitates 3D porous scaffolds made by ceramic solid-state electrolytes (SSEs). Herein, a general and facile method to sinter 3D porous scaffolds with a range of ceramic SSEs on various substrates at high temperature in seconds is reported. The high temperature enables rapid reactive sintering toward the desired crystalline phase and expedites the surface diffusion of grains for neck growth; meanwhile, the short sintering duration limits the coarsening, thus accurately controlling the degree of densification to preserve desired porous structures, as well as reducing the loss of volatile elements. As a proof-of-concept, a composite SSE with a good ionic conductivity (i.e., ≈1.9 × 10^-4 S cm^-1 at room temperature) is demonstrated by integrating poly(ethylene oxide) with the 3D porous Li_6.5 La₃ Zr_1.5 Ta_0.5 O₁₂ scaffold sintered by this method. This method opens a new door toward sintering a variety of ceramic-SSE-based 3D scaffolds for all-solid-state battery applications.

Rapid Synthesis and Sintering of Metals from Powders

Powder to bulk processes, such as additive manufacturing and metal injection molding (MIM), have enabled great potential for complex metal designing and manufacturing. However, additive manufacturing process normally introduces a high residue stress and textures due to the locally intense temperature. MIM is an excellent batch manufacturing process; nevertheless, it is not suitable for rapid screening and development of new metal compositions and structures due to the slow sintering process. Herein, an ultrafast high-temperature sintering (UHS) process is reported that enables the rapid synthesis and sintering of bulk metals/alloys and intermetallic compounds. In this process, elemental powders are mixed and pressed into pellets, followed by UHS sintering in just seconds at a temperature between 1000 and 3000 °C. Three representative compositions, including pure metals, intermetallics, and multielement alloys, are demonstrated with a broad range of melting points. The UHS process for metal sintering is nonmaterials specific, in addition to being extremely rapid, which make it suitable for materials discovery. Furthermore, the sintering method does not apply pressure to the samples, making it compatible with 3D printing and other additive manufacturing processes of complex structures. This rapid sintering technique will greatly facilitate the development and manufacturing of metals and alloys.

Computation-Guided Synthesis of New Garnet-Type Solid-State Electrolytes via an Ultrafast Sintering Technique

The discovery of new solid-state electrolytes (SSEs) can be guided by computation for next-generation Li batteries toward higher energy density and better safety. However, conventional synthetic methods often suffer from severe loss of Li and poor material quality, therefore preventing the promise of the predicted SSE candidates to be realized. In this study, computationally predicted SSEs with desirable material quality are synthesized via an ultrafast sintering technique. Three new garnet-type Li⁺ conductors, including Li_6.5 Nd₃ Zr_1.5 Ta_0.5 O₁₂ (LNZTO), Li_6.5 Sm₃ Zr_1.5 Ta_0.5 O₁₂ (LSZTO), and Li_6.5 (Sm_0.5 La_0.5 )₃ Zr_1.5 Ta_0.5 O₁₂ (L-LSZTO), are screened by density functional theory to exhibit good synthesizability and stability. The ultrafast sintering method by Joule heating effectively shorten the sintering time from several hours to <25 s, thereby reducing the Li loss and effectively merging the grains toward high material quality. In agreement with the computational prediction, LNZTO demonstrates the best synthesizability and phase stability, thereby achieving the highest conductivity of 2.3 × 10^-4 S cm^-1 among the three new SSE candidates. Using a current density of 0.2 mA cm^-2 , the Li/LNZTO/Li symmetric cell can cycle for ≈90 h without obvious increase of overpotentials. This study showcases the successful realization of computational predictions by the ultrafast sintering technique for the rapid optimization and screening of high-performance SSEs.